Would I be able to use an iPhone 5 from Sprint on my AT&T plan?
Nope. I have spoken to AT&T and other GSM carriers about this many times as well as Sprint and other CDMA carriers to see if phones purchased would be compatible. ALL of the companies said "no."
Ok thank you very much. From what I understand though you can use a Verizon iPhone 5 with an AT&T sim card in it?
Correct. You can swap the sim card from a Verizon iPhone 5 and it will function on the AT&T network.
You can sell the Sprint iPhone for some good money, and maybe even have money left over when buying a phone from AT&T at the 2 year contract price.
Great to hear thank you, Will an AT&T iPhone 5 work on Verizon then? Or does that have to be unlocked?
Would I be able to use an iPhone 5 from Sprint on my AT&T plan?
So if I get a Verizon iPhone 5 all I have to do is put my AT&T SIM card in the Verizon phone and it will work?