Can you buy an unlocked phone and make it a go phone with a go phone SIM card?

Sim Card SwitcharooMost phones that accept a SIM card can be unlocked and used for any service that uses SIM card technology. AT&T and Tmobile phones & SIM cards can be used in this way. However Tracfone and Net10 phones and SIM cards cannot.

For AT&T and Tmobile, Prepaid or Contract makes no difference. I use my ATT / Cingular contract service SIM in a T-Mobile Prepaid phone. (unlocked of course). The unlocking bit, depending on the company that makes the phone, can get a little tricky; but if you put some time into searching, you can find the information you need for a small cost or most likely free altogether. I am leaving out info pertaining to technology compatibility as most state and abroad phones are GSM, and you most likely have a GSM SIM card.