If you have a T-Mobile cell phone, you can use it with a T-Mobile prepaid SIM card even if you do not have a T-Mobile service contract. Simply purchase a SIM card, activate it and place it in your T-Mobile cell phone. Prepaid SIM cards are attached to credit card-sized plastic holders referred to as activation cards or SIM holders. You can activate a T-Mobile prepaid SIM card online using the information on the SIM holder along with the information printed on the cell phone.
