This video is specifically for the C530 Slate cell phone from AT&T, though this procedure will probably work on similar models of phone. You can hack, or jailbreak, your phone to allow you to use third party apps or switch to a different service provider. You will need a non-AT&T sim card for this hack to work (T Mobile is shown in the video). Then turn it on, hit the unlock key and then enter in your unlock code. Make sure you get it right!