okay so here's the deal:
But the
iPhone 4S supports both GSM and CDMA networks, and has a micro-SIM card slot no matter which carrier you subscribe to. So if you buy a phone from a CDMA carrier that doesn't use SIM cards, what’s in that slot? The answer is something that’s called a “roaming SIM.” If you're subscribed to a CDMA carrier in the states, when you travel internationally, your device can now switch to an international GSM network using a micro-SIM card. In other words, when outside the U.S., you can still get phone calls to your regular number and connect to the Internet, thanks to a micro-SIM that connects to Sprint and Verizon’s partner wireless networks in those countries—all at much higher rates than in the U.S., of course.
That’s essentially the experience AT&T iPhone customers have known all along. And because AT&T
iPhones are locked to the micro-SIM card in the slot, when you travel overseas, you’re forced to pay AT&T’s roaming charges.
But there’s a new wrinkle that potentially makes the international-roaming experience better on Sprint and Verizon iPhones than it is on AT&T. Sprint plans to sell the iPhone 4S with its micro-SIM slot unlocked; Verizon’s will be initially locked, but if you’ve been a customer in good standing for 60 days, you can call Verizon and ask for an “international unlock.” (A Verizon spokesperson told me that this is Verizon’s standard policy for all world phones—it’s just the first time it’s manifested itself on an iPhone.)
How international is the iPhone 4S 'world phone?' | Macworld
Apparently, verizon allows one customer to get only one phone unlocked like this once every ten months. So how are there so many iphones floating around on
ebay.