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SMS OTP delivered to WhatsApp instead of SMS for Pakistan (+92) numbers — using unregistered Sender ID

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I'm sending transactional OTP (sign-in verification codes) via Amazon SNS / AWS End User Messaging SMS from the eu-central-1 region, using an alphanumeric Sender ID for Pakistan (+92) destinations. Issue: The OTP codes are being delivered to recipients' WhatsApp instead of as normal SMS, and delivery is inconsistent.

What I've checked so far:

Account is out of the SMS sandbox with a production spend limit applied. SMS default type is set to Transactional. The Sender ID is created in the console but is unregistered for Pakistan. Sending is strictly transactional OTP, no marketing, no URLs.

Questions:

Is the WhatsApp rerouting caused by the Sender ID being unregistered for Pakistan? Pakistan is not listed in the self-service Sender ID registration countries — what is the correct process to register a Sender ID / alphanumeric mask for Pakistan so messages deliver as SMS? Is there anything else needed from my end (templates, registration, documents) to get reliable SMS delivery to Pakistan?

Any guidance from others who have successfully delivered OTP SMS to Pakistan would be appreciated.

Topics
Application IntegrationFront-End Web & MobileInternet of Things (IoT)Business Applications
Tags
Amazon PinpointAWS End User MessagingAmazon Simple Notification Service (SNS)
Language
English

asked 4 months ago183 views

1 Answer
2

As far as I know, Yes, the WhatsApp rerouting is directly caused by using an unregistered Alphanumeric Sender ID for Pakistan.

Here is why this is happening:

  • Carrier Blocking: The Pakistan Telecommunication Authority (PTA) strictly blocks unregistered alphanumeric masks (masking).
  • Aggregator Fallback: When AWS routes your message, downstream telecom partners realize the SMS will be blocked by local Pakistani carriers. To prevent a 100% delivery failure, these aggregators automatically intercept the message and reroute the OTP via the WhatsApp Business API using generic sender profiles.

To resolve this:

You must open an AWS Support Case (under AWS End User Messaging SMS -> Sender ID Registration) to manually register your Alphanumeric Sender ID for Pakistan. Once officially whitelisted by the PTA, your OTPs will deliver reliably as standard SMS.

EXPERT

answered 4 months ago

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