At any time in your T-Mobile contract or prepaid service, you can request a replacement SIM (Subscriber Identity Module) card. You will not be able to have two SIM cards registered to the same number at the same time. Once you order another SIM card, the previous one is automatically deactivated for security purposes. You can however, order a replacement card registered to the same phone number.
Call your wireless provider. Make sure to have your account details such as account number, phone number, name and address. Ask for a replacement SIM card.
Ask the agent to deactivate the other SIM card. At the same time, notify the agent as to whether the SIM card was lost or stolen.
Wait for the replacement SIM card to be mailed or if your wireless provider allows, you may be able to pick it up at a specific store.
If your handset was stolen and you are calling in to get a replacement SIM card, make sure that the new handset you are putting the replacement SIM in has the name of your wireless provider on it.