Hello! So I got myself a used HTC vivid and stuck my sim card that I had been using in my old LG thrive in the phone. All works as it should except for mobile data. I will turn mobile data on and it won't connect. J already have a data plan on the sim card. Does anyone know why this may be? Is it a problem with the phone or at&t? Do I need to contact them? Or can I fix it myself? (Preferred) Thanks! If you need any other info I would be glad to give it to you so long as its safe for me to do so.