Hello. I have an iPhone 3GS MC model running 3.1.3. I currently live in Korea but plan to travel to the United States for a month. Can I unlock this model? If I can, after I unlock it, what do I need to do? I tried to Google this, but I am still a little unsure as o what unlocking a phone actually does. Do I get a prepaid sim card from a US carrier? I think the problem is that I am unclear about what unlocking a phone does. Any help for this lost noob would be greatly appreciated. Thanks for the help!