End user is not receiving SMS text messages via AWS SNS Topic text messaging service

There are several potential reasons why your UX designer might not be receiving SMS messages via AWS SNS, even though the logs indicate successful transmission. This issue could be due to a combination of factors:

1. Carrier-specific restrictions: Even though you and the UX designer share the same carrier (Public Mobile), there might be differences in how messages are handled in different regions. Some carriers may have region-specific filtering mechanisms or security policies that could prevent certain types of messages from being delivered.

2. Phone settings: The UX designer's phone might have specific settings that are blocking or filtering out these messages. This could include spam filters, blocked numbers, or other security features.

3. Opt-in status: In some regions, recipients must opt-in to receive SMS messages from short codes, which are commonly used for OTP texts. Ensure that the UX designer's phone number is properly opted-in to receive messages.

4. Delayed delivery: SMS messages may experience delays due to network congestion or other factors. The message might eventually be delivered, but it could be delayed beyond the expected timeframe.

5. Network issues: Temporary network issues or outages specific to the UX designer's location could prevent the delivery of SMS messages.

To further investigate and resolve this issue:

1. Verify the phone number: Double-check that the UX designer's phone number is correctly entered in your system, including the country code.

2. Test with alternative numbers: If possible, have the UX designer try receiving the OTP on a different phone number to determine if the issue is specific to their current number.

3. Check carrier settings: Contact Public Mobile (or Telus Communications) to inquire about any potential restrictions or filtering that might be affecting SMS delivery for the UX designer's specific number or region.

4. Review AWS SNS logs: Examine the CloudWatch logs for the specific messages sent to the UX designer's number. Look for any unusual patterns or error messages that might provide more insight.

5. Enable detailed SMS event logging: If not already done, enable detailed SMS event logging in Amazon SNS to get more information about the message delivery process.

6. Consider alternative channels: As a temporary workaround, you might want to offer alternative authentication methods, such as email OTP or in-app notifications, for users experiencing SMS delivery issues.

If the problem persists after trying these steps, it may be necessary to open a support ticket with AWS. They can provide more specific insights based on your account configuration and work with the SMS providers to identify any underlying issues.

Sources
AWS SNS can not send SMS to mobile phone | AWS re:Post
Adding and verifying phone numbers in the Amazon SNS SMS sandbox - Amazon Simple Notification Service
AWS SNS - SMS not receive to mobile at some times | AWS re:Post