HT1937: iPhone: Wireless carrier support and featuresLearn about iPhone: Wireless carrier support and features
Currently Being ModeratedOct 7, 2012 2:33 AM (in response to moey12)
Call your carrier unless it is Verizon. Verizon doesn't use GSM on the iPhone 4 except for overseas. So, if it was ATT then call ATT and ask for unlock code. They will ask for your IMEI number which is found under Settings > General > About
Currently Being ModeratedOct 7, 2012 2:38 AM (in response to moey12)
I just saw the CDMA in your description. I don't believe an unlock will help you but I could be wrong.
Now, the iPhone 5 has an active SIM in the CDMA phones and already comes unlocked (Verizon only) and you can pop in an ATT SIM and use ATT service. But, I don't think you can do the same with the CDMA iPhone 4. Best to trade it in or use it on Verizon.
Edited to clarify that only Verizon iPhone 5 is unlocked as far as the SIM goes. It was FCC mandated.
Message was edited by: matrixxzero