Your gonna prolly end up paying close to 500 Anyways cause by the 30th day you would have to pay one billing cycle, the activation fees, the taxes and termination fee and unless your cancel it on the exact 30th day your gonna also pay prorated charges for the next month.....Your whole plan might just blow up in your face....AT&T doesnt play when it comes to iPhones.....
I advise others to not try this because of this example alone....