I am currently on Tmobile and wanted to buy the new iPhone 5S. I have over $700 in bestbuy reward certificates and gift cards. Bestbuy doesn't offer the tmobile version of the 5S, so could I buy the ATT one off contract (pay full price) and will they unlock it for me? What is the process to unlock the Iphone, now that they have said it is illegal to do unless it it from the manufacture or carrier. I know I could buy one directly from Apple but I would like to use my certificates and gift cards.