Just a q's if anyone has done it. I know the verizon carrier unlock your iphone 4s for international use but not for US GSM carriers

But just wondering if there's any way to use verizon CDMA iphone 4s on att since CDMA ones run on different modem firmware.

Can i upload a new IOS 5.0.1 from GSM section that would put the GSM modem firmware on it and use it on GSM carrier here in the US. Thx

Not possible yet. In theory, it's possible as the baseband supports both CDMA and GSM bands, but I know for a fact that Apple claims the GSM iPhone 4S CAN NOT work on CDMA, even though it has the radio baseband. No one has really been able to explain why, or whether that is actually true. With the (hopefully) impending A5 untethered jailbreak for 5.0.1, we may start seeing a lot more information about the baseband in the 4S which can help answer questions as to whether things are or are not possible.

At present, however, it is not possible to use a CDMA iPhone 4S on AT&T -- even if AT&T is willing to activate the phone, putting a MicroSIM in results in the same 'SIM not supported' error that you'd get on a standard, locked phone.

Attempting to restore the GSM iOS .IPSW to your phone will fail, it will tell you that it is not the correct build for your model device.