I live in Korea, where the carriers offer a free and legal country unlock. You have to give them the serial number and IMEI. However, due to the language barrier, the instructions after this are not as clear. They say to insert the foreign carrier's SIM card and then simply sync with iTunes. That's it. My question is how this works exactly, and what happens if I sync before I insert the SIM card. I won't be traveling for another month, and therefore won't have a new SIM. How can I be sure the unlock works once I am abroad?