I brought a Samsung Galaxy S7 Active device over from AT&T, but it appears that I'm not able to send MMS messages. Texting works as far as I can tell, but I also get a text from 94183571 every time I start the phone saying "Sorry, this service is not available." I'm thinking the two things are related.
I believe I have all of the APN settings correct because it looks like everything else on the phone works as intended. However, resetting the phone to defaults on the Access Point Names screen doesn't clear out everything as I would expect it to. There are 9 non-Ting settings that persist after I reset to default, including a T-Mobile IMS apn. I think this might be because the Galaxy S7 Active is exclusive to AT&T unless you unlock it. I have also attempted everything on the https://help.ting.com/hc/en-us/articles/205421078-Troubleshooting-GSM-Picture-Video-MMS-Messaging page multiple times.