Mobile phones provided by GSM cellular networks use a small memory unit called a subscriber identity module (SIM). That houses your phone's number, rate plan information, contacts, and text messages. You can swap out a GSM phone's SIM card at any time, but you will first need to program the card with your account information. To program a SIM card, you will need to contact your mobile phone provider and have them initiate an over the air (OTA) update that will be wirelessly transmitted to your phone.
Open your computer's web browser. Navigate to the Website for your mobile phone provider (see Resources). Click on the "Contact Us" link at the bottom of the Website. Note down the 800 number to contact the company.
Power off your cellular phone. Flip it over so that the back is facing upwards. Push down on the battery cover; slide it towards you to remove it from the phone. Set the battery cover aside. Slide a fingernail underneath the battery. Lift it straight upwards. Pull the battery out of the phone. Set it aside.
Pull the metal SIM card cover off of the SIM card. Pull the SIM card out of the phone and locate the identity number on the back, which should be between 16 and 19 digits. Write down the SIM card number and then reassemble your phone. Power the phone on.
Use a different phone to call the 800 number for your cellular provider that you noted down earlier. Provide the customer service representative with your name, mobile phone number and account number. Let him know you need to have your SIM card programmed. Give him the SIM card number you wrote down.
Ask the representative if you need to enter in a specific code on the phone for it to receive the OTA update. Enter the code in and wait for the OTA update to arrive. It will show up on your phone as a text message. Open the message and use the phone's arrow keys to highlight the option that is labeled as "accept update." Hit the menu or enter key on your phone to download the update and program the SIM card.
Your mobile phone account number can usually be found at the top of your monthly billing statement.