Here is a tutorial on how to unlock the Galaxy S3, so you can use it on any GSM network.

  1. Get your phone’s IMEI number by typing *#06# into your keypad. A screen will appear showing the code. Make note of this number for later use.
    unlock t-mobile galaxy s3 instructions

  2. Contact your network provider and request an unlock code. In some cases the network provider won’t supply the unlocking code till you have a certain amount of time with them (6 to 12 months). If your provider does not supply the code you can get it from an unlocking website.

  3. Get the unlock code over the phone (from your network provider) or from the email that you receive (from the unlocking website).

  4. Enter a SIM Card from a network that does not work with your mobile phone.

  5. Power your Samsung phone on. You will be asked for an unlock code.

  6. Enter the unlock code into your Samsung device and your phone should be unlocked!