I was considering moving our family plan from Sprint to AT&T due to Sprint's incredibly poor data speeds and horrendous connectivity problems in Poughkeepsie NY (where my daughter will be attending college). What has kept me from pulling the trigger so far are: 1. Cost. I pay $170 per month after my discount. I'd be paying $220 per month at AT&T and get slightly less in terms of services. 2. There are 3 iPhones on our family plan along with one basic flip phone. I don't want to deal with selling the Sprint iPhones and buying new AT&T iPhones. A rep at AT&T explained that if I got the Sprint iPhones unlocked, because they're all the 4s model I could simply use them on AT&T's GSM network. I've heard from other folks that an unlocked iPhone 4s will work on European networks but not on North American networks. Is this true?