I have an unlocked 521 and I want to use it on at&t network. I already have an at&t sim card with a different number than my current one. I tried inserting sim and I can call and receive calls on at&t but no mms or internet. Do I need to change something in settings to make this work on at&t?
Also will I be able to switch back and forth between tmobile and at&t?
Also will I be able to switch back and forth between tmobile and at&t?