A mobile phone connects and identifies itself to a mobile network through the subscriber identity module (SIM) card. If you would like to change to another mobile network, you have to use the SIM card to that network. The problem is that most mobile service providers lock the SIM application in their mobile phones to prevent you from using another mobile network. You have to unlock that SIM application with the unlock code to your handset before you start using a new SIM card.
Turn on your mobile phone. Dial *#06# and press the send button. Write down the IMEI number that appears.
Call your mobile service provider to request the unlock code to your mobile phone. Give them the IMEI number so they can determine the unique identity of your handset. Give them your e-mail address so they can send you the unlock code and the instructions.
Follow the instructions when you receive them through e-mail. When you see the unlock confirmation, turn off the mobile phone. Remove the battery door and battery. Remove the SIM card from your old mobile service provider.
Insert the SIM card to your new mobile service provider. Replace the battery and battery door. Turn your mobile phone on to connect to the new mobile network.
Depending on the mobile network and the mobile phone in question, you may not be able to access all of the features of your new mobile network with your unlocked handset. If you have questions, contact your new mobile service provider to guidance.