"Pay As You Go" is a program offered by multiple cell phone carriers, such as AT&T and T-Mobile, that allows the user to prepay for minutes without having a restrictive cell phone contract. Each wireless company offers different "Pay As You Go" plans. For example, you can prepay for minutes, or you can pay a flat fee each day you use your phone regardless of how many minutes you use. A SIM card stores your "Pay As You Go" information and personal information, including your address book.
Locate your SIM card number, which can be found on the white card that comes attached to your SIM card. For AT&T, the SIM card number begins in "89" and is the bottom number listed on the card.
For T-Mobile, you will need the IMEI number listed on the area of the phone where the battery is inserted, and the SIM card number found on the white card attached to the SIM card. The SIM card number is listed beneath the bottom bar code on the card.
Go to the AT&T Go Phone activation website (see link under "References"), if you have an AT&T SIM card. If you are using T-Mobile, you will have to register your SIM card over the phone.
Enter your AT&T SIM card number into the labelled blank on the Go Phone activation page. Click "Continue" when you are finished. Follow the rest of the prompts to activate your SIM card, including entering some personal contact information.
To register a T-Mobile SIM card, call 1-877-778-2107 from a different cell phone than the one you want to register. An automated system will help you register your SIM card. A text message will be sent to your phone to confirm activation.