When your T-Mobile SIM card malfunctions or you otherwise need to obtain a duplicate SIM card, you will need to visit your local T-Mobile branch, verify that you are an account holder and wait for the agent to duplicate the card. Once duplicated, you can use the card in your current T-Mobile phone or any other phone capable of using the T-Mobile network.
Locate a local T-Mobile branch (see Resources). Enter your address, search radius, T-Mobile location type, and press "Search." Bring your phone to the T-Mobile location during listed business hours.
Power off your phone. Tell the T-Mobile customer-service agent that you would like to duplicate your current SIM card. Be prepared to verify your account information, including your name address and billing information.
When prompted, remove the phone's battery and SIM card. The card is located behind your phone's battery. Slide the card out and give it to the agent.
Wait several minutes for the T-Mobile agent to copy the SIM card. The agent will place your card into a SIM-duplication device, insert a blank SIM and copy the data from the first card.
Place the new SIM card into the slot provided. Replace the battery and battery plate. Power on the phone by pressing the "Power" button. If the phone loads onto the T-Mobile network, your new SIM is working properly.