I am planning to make a move to AT&T, and given that the iPhone 5 might be the greatest thing ever in the universe, I would like to get it when it comes out. I need to transition to AT&T before that will happen, therefore I was planning on picking up an older iPhone from eBay or wherever and using that until the 5 is released. So, my question is: Will that work? Will they let me as a new customer come with my own phone such that I can get the contract price for the new phone when it is released? Thanks!