AWS SNS SMS being redirected to WhatsApp in Nepal – message substitution or delivery issue?

Question

Hey there,

We're facing issue sending SMS to international clients. Some of the clients in Nepal are reporting that they're receiving an Whatsapp message in their phone number (from contact name ADA OTP) saying `**** is your verification code....` Instead of the original (different) message sent from AWS SNS to their phone number.

Although the AWS SNS console and log marks it as Succcess. The end users are not receiving (sometimes yes sometimes no :D) the SMS.
FYI: We did capture an error once like

```
{
    "notification": {
        "messageId": "12fdb123-78c8-5670-b83f-d1fd86c9cbdf",
        "timestamp": "2025-07-02 09:28:33.536"
    },
    "delivery": {
        "phoneCarrier": "Nepal Telecom",
        "mnc": 1,
        "numberOfMessageParts": 1,
        "destination": "+<977>...",
        "priceInUSD": 0.2327,
        "smsType": "Transactional",
        "mcc": 429,
        "providerResponse": "Unknown error attempting to reach phone",
        "dwellTimeMs": 33,
        "dwellTimeMsUntilDeviceAck": 2594
    },
    "status": "FAILURE"
}
```

If you can share what's happening here, it would be great. Thank you

re:Post Agent · Answer

Based on your description, it appears you're experiencing an issue where SMS messages sent through AWS SNS to recipients in Nepal are being inconsistently delivered, and in some cases, being replaced with WhatsApp messages from a contact named "ADA OTP" containing verification codes.

This situation suggests several possible issues:

1. Carrier Intervention: Mobile carriers in Nepal might be intercepting certain types of SMS messages (particularly those that appear to be OTP/verification codes) and redirecting them through WhatsApp or other messaging services. This is sometimes done by carriers to reduce costs or manage network traffic.

2. Third-party Interception: There could be a service or application on the recipients' phones that's intercepting SMS messages and redirecting them to WhatsApp.

3. Message Delivery Issues: The error log you shared indicates a failure with the provider response "Unknown error attempting to reach phone" for Nepal Telecom. This suggests there are connectivity or delivery issues with the carrier in Nepal.

To troubleshoot this issue:

1. Enable comprehensive SMS delivery status logs in CloudWatch if you haven't already done so. This will help you track the delivery status of all messages.

2. Check if this issue is specific to certain types of message content (like OTPs) or affects all messages to Nepal.

3. Test sending messages with different content to see if that affects delivery.

4. Consider reaching out to AWS Support with specific message IDs and timestamps of the affected messages. They can investigate the delivery path more thoroughly.

5. If possible, contact Nepal Telecom to inquire if they have any policies regarding SMS redirection to WhatsApp or other messaging platforms.

The inconsistent delivery (sometimes working, sometimes not) is a common characteristic of carrier-related issues, which aligns with the error message you received about an unknown error attempting to reach the phone.  
**Sources**  
[AWS SNS is sending weird SMS | AWS re:Post](https://repost.aws/questions/QUe6OXU0GBQ8uj1xQBDIQLPQ/aws-sns-is-sending-weird-sms)  
[AWS SNS can not send SMS to mobile phone | AWS re:Post](https://repost.aws/questions/QUVa9lqxT9SeWWTnuZvcrZvQ/aws-sns-can-not-send-sms-to-mobile-phone)  
[Pinpoint SMS delivery failure after the latest PE-TM binding process, despite receiving a SUCCESSFUL API response. | AWS re:Post](https://repost.aws/questions/QUD8QUW8d_RRuAx03E4LjQcQ/pinpoint-sms-delivery-failure-after-the-latest-pe-tm-binding-process-despite-receiving-a-successful-api-response)  
[Amazon SNS SMS delivery monitoring with Amazon CloudWatch metrics and logs - Amazon Simple Notification Service](https://docs.aws.amazon.com/sns/latest/dg/sms_stats_cloudwatch.html)

AWS SNS SMS being redirected to WhatsApp in Nepal – message substitution or delivery issue?

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