Block SMS from Fast2SMS users:
Click 'Block' button to block messages from Fast2SMS users.
Block Messages From Fast2SMS:

Enter the verification code sent on your mobile number:

Click 'Check' button to verify whether you've blocked messages from Fast2SMS:
Check block SMS From Fast2SMS:

Click 'Unblock' button to get messages from Fast2SMS:
Unblock SMS From Fast2SMS:

Enter the verification code sent on your mobile phone