I have an iPhone 4 that I would like to swap out with an iPhone 5. I know that the iPhone 4 uses a micro sim and the iPhone 5 uses a nano sim. I can attempt to cut the sim myself and don't tell AT&t, but would it cost me anything to take it into an AT&T store and ask them to give me a new sim card and transfer the phones? Will they charge me an upgrade fee if I tell them or is this a service that they provide for free? In addition, both phones are not under contract.