Hey there lbyeager. I have a couple of suggestions. I would try restarting the phone. After it comes back on, try reconnecting to T-Mobile's networking by doing a Manual network selection using the steps in the link below.
Once you're connected, test the messaging with multiple numbers to see if they go through.
29 Mr 2016
Dear Mike C:
Thanks to your kind encouragement I did some more experimenting and
discovered, belatedly, that the bothersome message was simply an
ordinary text message of March 3 from someone identified by no more
than "40". What explains that? Anyway, I just deleted that message,
and the phone now works for
both outgoing and incoming texts.
Thanks for keeping me posted. I'm really glad that pesky message is gone and you're messaging is back to normal. If the message came from the number 40, this could have been some kind of spam message. (Not one I'm familiar with though) Any-who, it's just awesome to hear that it's working.