maamoun wrotehere's the deal with Iphone 4S, NEVER buy a Verizon phone from the US, it will NOT work in Lebanon no matter what you do, it doesn't even use the GSM technology, it uses some older CDMA proprietary wireless protocol. you can buy an unlocked Iphone 4S from Apple store, you will save a $100 to $150 (they sell for $750 in Lebanon for 4S 16G) and there is no need to do anything with it, just make sure you do not register it in the US, bring it here in the box and register it to a lebanese network using a lebanese SIM. OR, better yet, get an AT&T locked phone real cheap and you can unlock it at any Cellular shop here for less than $20.
If I'm not mistaken, i think the iPhone 4S is dual networked having GSM and CDMA. So as long as its unlocked you should have no problem.
