IMO you'd be far better served to simply purchase a prepaid package while there that includes the phone and SIM. It's not much more money but will be far more convenient. That way you don't have to keep track of where your sims are and swap them out. Cingular is a pain to get unlock codes from. For former AT&T Wireless numbers/phones I've had zero luck. For Cingular numbers, it's taken numerous followup calls and several weeks but I have gotten two phones unlocked. IMO it's just not worth the effort when prepaid packages are so inexpensive.