[Q] Boost S3 can't receive SMS/MMS from specific people/person topic

I have a friend who I've been texting since December 2014 and suddenly today they stopped receiving the messages from me. Messages can be received from others, but not from me. I'm not on any block list or anything. I've tried sending pics and they also don't work. I've tried sending messages to other people and they say they receive the message right away. I'm using ATT GoPhone with a Nexus 5 they have Boost with an S3.

I'm using Cataclysm 5.0.2 and they use stock Android 4.4.2 from Boost.

I've tried explaining how to find the APN settings but they said they can't find it anywhere.