If your iphone is with Sprint and you are or were a customer in good standing, you can call them and tell them you are China and would like the gsm portion of your iphone unlocked. After a restore on itunes, your iphone would be unlocked. My cousin did this recently and it worked, but he had to call sprint 3 times, because the first two agents only wrote notes about the order to unlock, but never actually sent the order into their system.