My brain can never seem to comprehend this subject whenever someone in my family needs a new phone. We have AT&T Sim cards in our phones. We do not have a contract. Can I buy ANY unlocked phone and put my AT&T Sim in it and have it work? I'm guessing the answer to that is no since the phones I am looking at say things like, "No contract, unlocked" but then they say T-mobile some other carrier. We used to have contract Verizon phones years ago and I got rid of those because I was always told they were the one carrier that was never interchangeable. Now we have these AT&T go-phones and I believe I am still committed to only buying something that is specifically meant for AT&T, right?