My Goal: To land in any country on earth (with exception of Japan, etc), pop in a local SIM card, and have a local phone number while visiting that country. My Needs: 1) I would need an iPhone 4 (AT&T version with sim card slot) correct? 2) I would need to unlock this phone, correct? 3) If this phone is unlocked, it can be used with pretty much any SIM card in any country worldwide, giving me a local phone number there, on the prepaid sim? 4) I see a lot of unlocked iPhone 4 on Amazon.com but they run $750+. Would it be cheaper to just buy an iphone 4 and unlock it myself? 5) I was told its a royal pain in the ass to unlock an iphone 4 ... true?