if you need to unlock any gsm cell phone, try newmobilefreedom.com: http://www.newmobilefreedom.com

An "unlocked" cell phone is where it has been modified to accept different carriers. (i.e. Cingular, TMobile, Verizon, etc) So in the case of you selling/buying an "unlocked" cell phone, that would mean people who have different carriers could use the phone with their current SIMM card. Most carriers use the SIMM card technology - I know Sprint does not use SIMM cards, so an unlocked phone would not work with Sprint. Hope this helps!

I'm glad you asked because I see that too and I always wondered, so I'll be watching for someone to answer this. I have an old cell phone that I could sell but I don't know how it becomes "locked" or "unlocked"?? Thanks again and hopefully someone will know:)