Hello. I work for a company that builds white label chatbots for financial institutions. One of the channels we offer the service on is SMS, leveraging twilio as our provider to enable delivery of SMS messages.
I use my T-Mobile phone for receipt of inbound messages to test and demonstrate our technology. Recently, I'm experiencing behavior where the same exact messages in specific multi-part conversations will fail to reach my phone. Looking at twilio's SMS logs for these undelivered messages, they show a status of delivered to the carrier network (in this case that's T-Mobile).
I asked another individual with T-Mobile to test as well and he experienced the same behavior (same missing messages). But my colleagues with other carriers are able to receive all the messages on their phones without issue. One additional note is that if I modify the text in the missing messages to remove certain key words or phrases, those new messages WILL be delivered to my phone successfully on a subsequent attempt. If I restore the text to the 'undeliverable' version, it will fail to reach my phone again. So at this point it appears something internally on T-Mobile's end is preventing delivery of very specific messages in a 100% reproducible way. Spam blocker has already been disabled for my account, and customer support has been adamant that there's nothing else which which would prevent messages from being delivered.
I've spoken to multiple T-Mobile technical experts about this issue and opened at least a couple support tickets. I've received automated texts telling me the issue is resolved but no personal follow-up from any technical contacts at T-Mobile, and unsurprisingly the issue is not resolved.
At this point I'm reaching out on behalf of myself personally (As a customer/recipient, I wonder why I can't whitelist all messages from a specific number regardless of what internal anti-spam countermeasures that number might be triggering)... and on behalf of my company (As a legitimate service delivering messages on behalf of established, FDIC-insured financial institutions, we'd like to better understand the reason specific messages might not be delivered to mobile end users).
I've offered additional details and availability for joint troubleshooting to T-Mobile support. I can provide the originating phone number, my (inbound) T-mobile number, message SIDs, timestamps, and precise text for the missing messages. I'd hope all that information could enable you to to find some logs on the missing messages and determine a root cause. This issue is impacting me negatively on multiple fronts. I'd appreciate any assistance.