i'm no expert and have no proof, but i'm willing to bet AT&T won't let you get an iPhone if you've only had service for less than a month without surrendering your equipment. they know people will make a fortune off reselling the phones and they'll be losing tons of money. they're in business to make money. i'd be very surprised if you can sign up today and get a blackberry, then go back on friday and get an iphone and them just starting the contract over and letting you keep both phones, unless you're paying for 2 plans.