Hi folks. I'm relatively new to AT&T, having just switched from a Sprint 4S to a new 5c. So far, I love the new phone and even better, the network. Being new to SIM cards and GSM in general, I have a couple of questions about hypothetically getting a new phone next year. I'm not on AT&T Next, because I know I wouldn't save any money that way. If I were to buy the iPhone 6/6c/whatever when Apple inevitably releases it next year, it seems there are two options: buying locked from AT&T and buying unlocked, contract/subsidy free. I would resell my current phone to recoup costs. 1. Is it really as simple as swapping the SIM cards in the phone? Do I have to contact AT&T at all? 2. Can AT&T "see" that I have a new phone? Do they charge another "activation fee" or an "upgrade fee" of any kind to do this? 3. I've read that iPhones have their own data plans, which I know nothing about. Since I'm changing from iPhone to iPhone, I assume there would be no plan changes? 4. If you switch to an unlocked phone or unsubsidized phone, does AT&T extend your contract? I'm on a single-line plan, no conflicting upgrades or cross-line upgrades to worry about. From what I've read, it seems to be as simple as swapping the SIM cards. Based on my experience over the years of swapping phones with Sprint, I know sometimes the headaches are in the details (plan swaps, prorated bills, mysterious upgrade fees appearing) and it's hard to believe that AT&T is anything but. Thanks for clarification.