Wouldnt i have to transfer the 2year agreement to it?
Call *639# on the iPhone, you will received a message telling you if you're eligible for an upgrade or not. If not you will have to buy an unlocked one. :\
You can do an early upgrade, it will cost you $250 more to the contract pricing. You can also trade your 4s and get store credit to your new device.
I'm an AT&T employee. Feel free to ask any Qs.
I have a question
If I want to change my SIM card for a nano-SIM (you know using the same number) how much I have to pay? And also changing a nano-SIM to a normal SIM for an iPhone 4S.