Bulk Voice Call (OBD) Service in India: Price, Uses and Setup

A bulk voice call, also called OBD (outbound dialling), plays a pre-recorded message to thousands of phone numbers at once. On Fast2SMS you upload an MP3 or record the audio, upload your numbers from Excel or CSV and send the campaign, and at the time of writing you pay ₹0.25 per 15-second pulse only for calls that are answered. Missed, busy, switched-off and DND calls cost nothing, and any such debit is refunded to your wallet automatically within 48 hours. Promotional calls reach Non-DND numbers between 9 am and 9 pm, while reminders, alerts and OTPs reach every number at any time.

This guide explains how bulk voice calling works, what it really costs, how to record a message people listen to, the rules for DND and calling hours, Voice OTP, IVR and cloud numbers, election and business use cases, and how to set up your first campaign.

What is a bulk voice call (OBD)?

A bulk voice call is an automated phone call that plays the same recorded message to a long list of numbers. You prepare the audio and the list once; the platform dials every number, plays the message when the person picks up, and records whether each call was answered, missed, busy or blocked. In the telecom industry this is known as OBD, short for outbound dialler or outbound dialling, because the calls go out from the business to the customer. You will also hear it called voice broadcasting, voice SMS, robocalling or an automated voice call service.

It is worth separating four related services, because people often mix them up:

Fast2SMS offers all four from one voice call panel, in the same account and wallet you use for SMS, WhatsApp and RCS.

How an OBD campaign works

Behind the scenes, the platform reads your list, removes duplicates and invalid numbers, and for promotional campaigns checks every number against the national DND registry before dialling. The calls are placed; when someone answers, the audio starts playing and the clock starts. The duration from pick-up to hang-up is rounded up to the next 15 seconds to count pulses. Calls nobody picks up are recorded as missed or busy and cost nothing. The report updates in real time while the campaign runs.

Why voice calls still work in India

• A call is heard even by people who never read SMS. Many customers skim past text messages, but very few ignore a ringing phone.
• It works on every phone. Feature phones, landlines and smartphones with a full or filtered SMS inbox all receive a voice call. No app or internet is needed.
• Any language, any reading level. You record the audio yourself, so Hindi, Marathi, Gujarati, Tamil, Telugu, Kannada, Bengali or any dialect works equally well. Customers who are more comfortable listening than reading get the message in their own words.
• It feels personal. A familiar voice from a school principal, a doctor's clinic or a local shop carries more weight than plain text.
• Phones are always nearby. Fast2SMS's help guide notes that more than 90% of people keep their phones with them all day.

Voice is not a replacement for SMS or WhatsApp; it complements them. The best results usually come from sending the details by text and using a short call to make sure the message is actually noticed.

Bulk voice call price: pay only for answered calls

At the time of writing, Fast2SMS bills bulk voice calls at ₹0.25 per 15-second pulse, and only for calls that were answered. There is no setup fee and no monthly platform fee for bulk calls or Voice OTP. You recharge from ₹100 and pay as you go, and new accounts get ₹50 free credit to test.

How to estimate a campaign

Multiply the number of answered calls by the average pulses per call by ₹0.25. Fast2SMS's own example: 10,000 calls, of which 6,842 are answered, averaging two pulses each, comes to 13,684 pulses, or ₹3,421. The 3,158 missed and DND calls cost nothing. A customer who hangs up after six seconds still counts as one pulse, because the call was answered.

Two practical conclusions follow. First, the length of your audio matters more than the size of your list: a 14-second message costs half as much per answered call as a 20-second one. Second, you never pay for numbers that did not pick up, so you can retry them later without wasting money.

Refunds and what is not charged

Operators sometimes confirm a call's final status hours after a campaign. Fast2SMS reconciles every campaign against the operator's final records, and any amount debited for a call that was not answered comes back to your wallet automatically within 48 hours. Each refund appears in Transaction History with the campaign name. Duplicates and invalid numbers are removed before dialling, so you do not pay for them either.

Cloud number, IVR and agents

A cloud number has a monthly rental per number, shown in the panel when you request one, plus the usual per-pulse charge for call minutes. The drag-and-drop IVR flow builder and any number of agents and call groups are free. For several numbers or high volumes, contact sales for a custom rate.

DND and calling-time rules for bulk voice calls

Voice calls follow the same idea as SMS: marketing is limited, important information is not. The panel applies these rules for you, so a campaign is not rejected or wrongly charged.

If you schedule a promotional campaign outside the window, it is held and dialled from the next permitted time. Fast2SMS's older help guide gave the promotional window as 10 am to 9 pm; the current voice call page says 9 am to 9 pm, and the panel enforces whichever applies, so you do not need to track it yourself.

Other points to keep in mind:

• No DLT registration is required for voice calls, according to Fast2SMS's help guides. That makes voice one of the fastest channels to start with.
• Identify yourself. Say who is calling at the start of the message. A clear identification is part of calling legally in India.
• Transactional means informative. Do not slip an offer into a reminder to reach DND numbers; keep marketing on the promotional route.
• No personal, spam or fraud calls. The service is for business use, and campaigns that look like spam or fraud are not allowed.
• Offer an opt-out. Respect people who do not want further calls and remove them from your lists.

More on DND is on Fast2SMS's DND page.

Step by step: your first bulk voice campaign on Fast2SMS

1. Create a free account. Sign up at fast2sms.com with your mobile number. ₹50 credit is added so you can test a voice call or a Voice OTP straight away.
2. Recharge when ready. Add money from ₹100 by UPI, card or net banking. There is no pack to buy and no monthly fee.
3. Open the Voice section from the left menu of the panel.
4. Add your audio. Upload an MP3 or WAV file, use a text-to-voice file, or record the message directly in the panel. Preview it before moving on.
5. Add the numbers. Type a few numbers, or upload an Excel or CSV sheet for a large list. Duplicates and invalid numbers are removed before dialling.
6. Pick the type. Choose promotional for marketing (DND numbers are scrubbed automatically) or transactional for reminders and alerts that must reach everyone.
7. Send now or schedule. Pick a date and time inside the permitted window if you want the calls to go out later.
8. Confirm. A confirmation box shows the campaign details. Fast2SMS's help guide says new voice messages are checked by the team before release and approval can take 12 to 24 hours, so upload important campaigns early.
9. Track the report. Watch answered, missed, busy and DND counts update live, then retry the missed numbers with one click if you need to.

The full screen-by-screen process is in the help article how to send bulk voice calls, and common questions are answered in the voice call FAQs.

How to record a message people listen to till the end

Most listeners decide within the first few seconds whether to stay on the line. Because every 15 seconds is a pulse, a tight message is both more effective and cheaper.

A simple script structure

1. Who is calling (2 to 3 seconds): "Namaste, this is Demo Clinic, MG Road."
2. The one thing you need them to know (6 to 8 seconds): "Your appointment with Dr. Mehta is tomorrow at 4:30 pm."
3. What to do next (3 to 4 seconds): "To change it, please call us on the number in our SMS."

That message fits comfortably in one pulse. Promotional messages work best within 15 to 30 seconds, and transactional reminders are usually 15 to 20 seconds.

Sample scripts

Recording tips

• Use a clear, professional voice or good-quality text-to-speech. Speak a little slower than normal conversation.
• Avoid background music and noise. Fancy effects make the words harder to follow on a phone line.
• Repeat the critical detail once, such as a date, an amount or a code.
• Record one version per language and run separate campaigns for each regional list.
• Put your callback details in the message or in a follow-up SMS. Fast2SMS's older help guide notes that promotional calls may show a random caller ID, so customers cannot always call the displayed number back. If you need a fixed caller ID, ask about a cloud number.
• Preview before sending. Listen to the final file in the panel, exactly as customers will hear it.

Reading the call report, retrying and understanding failures

Open any campaign and every number is listed with its status (answered, missed, busy, switched off or DND), the call duration, the number of pulses and the exact charge. Missed calls show ₹0. Summary counts update in real time, you can filter by route, date and time, and the whole sheet exports to Excel. Each campaign also has an entry in Transaction History.

To reach people who did not answer, select the missed and busy numbers and launch a retry campaign with one click, or schedule it for a better time of day. Only the calls answered in the retry are charged.

Why calls fail

Fast2SMS's voice FAQ lists the usual reasons a call does not connect:

• Invalid or unallocated number.
• Subscriber not available, switched off or out of coverage.
• No response from the handset, or the phone cannot receive incoming calls.
• Network failure or congestion at the operator.
• Call timed out after all retries, including retries through different operators.

None of these cost you anything under answered-only billing. If the same numbers fail campaign after campaign, remove them from your list.

Voice OTP API: codes that reach every phone

Voice OTP is a one-time password delivered by an automated call that reads the digits aloud, twice, so the customer does not need to ask for a repeat. It reaches feature phones, landlines and customers whose SMS inbox is full or filtered. Most businesses use it as a fallback when an SMS OTP has not arrived within a few seconds, and some use it as the first choice for older or voice-first customers.

Voice OTP runs on the same Smart OTP API as SMS and WhatsApp OTPs. You create an OTP template in the panel (Smart OTP, then Templates) and set its channel to Voice call. Your app then sends one request:

curl -X POST https://www.fast2sms.com/dev/otp/send \
  -H "Authorization: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"mobile":"9999999999","otp_id":"YOUR_VOICE_TEMPLATE_ID",
       "otp_length":6,"otp_expiry":10}'

Fast2SMS generates the code, places the call within a few seconds and stores the code. When the user types it in, your app calls POST /dev/otp/verify with the mobile number and the OTP. You never store or compare codes yourself. A fallback channel can be set on the template, so a missed voice call can be followed by an SMS or WhatsApp OTP automatically, or the other way round. Pricing is the same pulse rate, answered calls only, and most OTP calls finish inside one pulse.

Code samples for PHP, Node, Python, Java and .NET are at docs.fast2sms.com. Compare channels on the OTP SMS page and in the WhatsApp OTP API guide.

Cloud number, IVR flow builder and agents

Bulk calls go out; a cloud number brings calls in. A cloud number, also called a virtual number, is a business phone number hosted on the platform. When customers call it, your IVR answers, plays a welcome message and a menu, and routes the call to the right person. Your agents can also place outgoing calls that show the same number, so customers always see one consistent business number.

• IVR flow builder: build the welcome audio, key-press menus and sub-menus, routing to an agent or a ring group, voicemail, and business-hours and holiday rules by dragging blocks. Change the flow any time.
• Agents and ring groups: add agents with their mobile or desk numbers, group them, and ring them in round robin or all at once. Agents and groups are free, however many you add.
• Recording and logs: every call is logged with time, direction, agent and duration, and recordings play back in the panel.
• KYC: operator rules require basic business KYC such as PAN or GST and an address proof before a number is activated. The team collects these during onboarding, and activation usually takes one to three working days.

A cloud number pairs well with bulk calls. Your campaign tells customers about an offer or a pending payment, and when they call back, the IVR sends them straight to sales or collections.

Bulk voice call use cases by sector

Payment reminders and collections

Lenders, NBFCs, finance companies, utilities and subscription businesses call every borrower or customer a day before a due date. Because these are transactional calls, DND numbers are reached too. A short, polite reminder with the amount and the due date, followed by a payment link on SMS or WhatsApp, recovers more on time than text alone. Pair it with a cloud number so customers who call back reach your collections team directly.

Appointments and healthcare

Clinics, diagnostic labs and hospitals call patients the evening before an appointment, or when a report is ready. Patients who do not read SMS still turn up on time, and a 15-second reminder costs one pulse per answered call.

Schools, colleges and coaching institutes

Holiday notices, exam schedules, PTM dates and fee reminders reach every parent at once, in the local language, recorded by the principal or class teacher.

Marketing and sales

Retail stores, real estate developers, education counsellors and event organisers announce festival sales, site visits, admissions and launches to their Non-DND customer lists between 9 am and 9 pm. Keep the message under 30 seconds and end with a clear next step.

Alerts, notices and confirmations

Housing societies, government offices, NGOs and service businesses use voice for notices that must reach everyone: a water cut, a meeting, an emergency change of plan, or delivery and order confirmations.

Fast2SMS's help articles on what bulk voice call is and the automated voice call service list more message ideas for each route.

Bulk voice calls for election and political campaigns

Voice calls are popular for election campaigns because a recorded message from a candidate, in the voter's own language, reaches every type of phone in a constituency. Typical uses are rally and meeting announcements, introductions of the candidate and party, reminders of polling day and booth details for supporters, and thank-you messages after the result.

A few practical points for planning a political voice campaign on Fast2SMS:

• Plan it under promotional rules. A campaign appeal is not a reminder about an existing transaction, so expect calls to reach Non-DND numbers only, within the 9 am to 9 pm window.
• Talk to the team first. For a large election campaign, book a call at fast2sms.com/meet so the right route, approval timing and volume are sorted before the dates that matter.
• Upload early. Voice messages may be reviewed before release, so do not leave the audio until the last day.
• Record region by region. Separate lists and recordings per area or language work better than one generic message.
• Keep it short and identify the sender at the start of the message.
• Use answered-only billing to your advantage. Retry missed numbers at a different time of day without paying for the ones that did not pick up.

Election campaigns are also subject to the rules of the election authorities, which are outside the scope of this guide; check them before you launch.

Voice calls vs SMS vs WhatsApp vs RCS

Each channel has a job. A good pattern is to send the details on SMS or WhatsApp and follow up with a short call for customers who did not respond. The Campaign flow builder automates this: SMS first, then WhatsApp, RCS or a voice call based on delivery, with delays between steps. Read the bulk SMS guide, the bulk WhatsApp guide and the RCS business messaging guide to plan the other steps, and see SMS pricing for text rates.

Mistakes to avoid in bulk voice campaigns

1. Long audio. A 50-second message costs four pulses per answered call and most people will not hear the end. Cut to the essentials.
2. Not saying who is calling. Unidentified calls get cut in the first seconds and erode trust.
3. Marketing on the transactional route. Offers belong on the promotional route, with its DND and time limits.
4. Poor recordings. Background noise, music or a fast speaker make the message hard to follow on a phone line.
5. Calling at the wrong time. Even for transactional calls, early mornings and late nights annoy people.
6. One message for every region. Record in the language your listeners actually use.
7. Leaving campaigns to the last minute. Allow time for review before time-sensitive campaigns such as sales or polling-day reminders.
8. Ignoring the report. Retry missed numbers, and clean numbers that fail every time.

Why choose Fast2SMS for bulk voice calls

• You pay only for answered calls. Missed, busy, switched-off and DND calls cost nothing, and any wrong debit comes back automatically within 48 hours.
• Short 15-second pulses at ₹0.25 at the time of writing, with no setup fee and no monthly platform fee for bulk calls or Voice OTP.
• Start small. ₹50 free credit after signup, recharge from ₹100.
• Simple panel. Upload or record audio, upload Excel or CSV lists, schedule, preview and retry missed numbers with one click.
• Automatic DND scrubbing and calling-window checks on promotional campaigns.
• A real per-number report with status, duration, pulses and charge, exportable to Excel.
• Voice OTP on the Smart OTP API, with SMS or WhatsApp fallback.
• Cloud numbers with a free IVR builder and free agents.
• One account for every channel: bulk SMS, WhatsApp Business API, RCS and voice share one wallet.
• Since 2011, with ISO 27001, SOC 2 Type 2 and VAPT-tested infrastructure, and support by chat, phone on +91 6262778822, email at [email protected] and free meetings.

Create your free account at fast2sms.com, upload a short message and test it on your own phone with the free credit. When it sounds right, upload your list and send.