So I am most likely going to leave AT&T after my contract is up in about a year. But I am still buying the new iPhone - unlocked. My question is how do I get the phone on to my account? Does the phone come with a new nano-sim? Buying unlocked I assume it won't be tied to my AT&T account in any way, so how does this work? Did anyone buy a 4S unlocked and have some experience?