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Couple of things -
An AT&T iPhone doesn't have CDMA which is what it would need to even work on Verizon. Also, Verizon will not activate any device that is not specifically for Verizon. So even if you had a Sprint iPhone with CDMA, Verizon still would not allow it.
The 4S is dual CDMA/GSM. It's the first iPhone of it's kind, everyone is using the same model. Theoretically it could work, the carriers just won't allow it.
Why don't you just ask Siri?
If you bought the phone outright you can use it on whatever carrier you like. If you got it subsidized then no, you can't. And by that I mean if you paid $750 for it.
If you bought the phone outright you can use it on whatever carrier you like. If you got it subsidized then no, you can't. And by that I mean if you paid $750 for it.
Unlocked iPhone 4S's from Apple can only be used on GSM carriers. The CDMA radio is only "on" for CDMA carriers like Verizon and Sprint.
I think the only way to get a true unlocked one would be if you got a Verizon/Sprint iPhone 4S and jailbroke/unlocked it to use on any GSM carrier. If that is possible.
Edit - Not sure what the guy is talking about in the story linked above. It says right on Apple's website that the unlocked iPhone 4S will not work on a CDMA network. And paying full price for a phone from any carrier (in the US) has never meant you were getting an unlocked one; just that you don't have to sign a contract.
The 4S is dual CDMA/GSM. It's the first iPhone of it's kind, everyone is using the same model. Theoretically it could work, the carriers just won't allow it.
It's got a dual radio in it for overseas travel. It'll work on a GSM carrier in Europe for instance but it won't work on American GSM carriers. My Storm2 was dual GSM/CDMA and could only be unlocked to work on foreign GSM carriers.
Your right about the iPhone but wrong about the BlackBerry, I had a Storm and Storm 2 and I unlocked them both and used them on both AT&T and T-Mobile.
On AT&T you never got anything more than EDGE did you? You never got 3G?