Double Message

[Android Central Question]

Hello! My phone has a problem. Everytime I am in a group chat it shows the recipients' names plus my own number (literally just a number). Normally, it would only show the recipients' names. Therefore, when I respond to the thread, my message sends, then I receive a message from my own phone. The recipients in the thread do not receive my message twice. It is just me. Moreover, everytime I receive a MMS or an image in a regular thread (with one recipient and myself) a new thread opens up just for that MMS/image then other messages (SMS messages) are received in the original thread. This has been messing up ever since my carrier switched my Sims card because of some update in the system. I do not know what to do. I have tried everything I can think of to fix this. It's really annoying.