Voice SMS: What It Is and How to Block It
Voice SMS delivers a recorded clip as a phone call. Here is how it works and how to stop it.
What is voice SMS
Voice SMS is a hybrid of a phone call and a text message. Instead of typing a message, a gateway places an outbound call to the recipient and plays a pre-recorded audio clip. The recipient sees an ordinary incoming call, picks up, and hears the message.
The format exists because of a practical problem: voice is far more likely to be actually listened to than a text. Several Indian banks and financial institutions use it for OTP delivery precisely because a call that a customer picks up is more reliably received than a text buried in a busy inbox.
Why it is misused
The same delivery mechanism used for bank OTPs is cheap to abuse. Marketing agencies rent voice gateways and push recorded promotional messages to lists of numbers, which is why a volume of unexpected automated calls appears in most Indian metro areas.
There is one thing worth distinguishing. A transactional voice call from your bank has a registered DLT sender ID and calls from a known number. A promotional flood almost never does. If the call is from a withheld or unknown number and delivers an offer, it is marketing, not your bank.
- Bank and transactional voice calls use a registered DLT sender ID
- Promotional voice floods use withheld or rotating virtual numbers
- Transactional calls are short, factual, and reference a specific transaction
- Promotional calls are longer, conversational, and lead to a callback or a link
How to block it
Start with the National Customer Preference Register, which is the only mechanism that covers promotional voice calls categorically. Beyond that, your carrier's verified caller screening handles unknown numbers, and Android's built-in call screening gives per-number control.
Our protection checklist covers all eight steps in order, including the specific settings to change and the escalation path if calls continue.