Swapping Subscriber Identity Module, or SIM, cards lets you move your cellphone service and number over to a different phone. SIM cards are used on Global System for Mobile Communications (GSM) and Integrated Digital Enhanced Network (iDEN) phones, but SIM cards are not exchangeable between the two services. Major GSM networks in the United States include AT&T and T-Mobile, while major iDEN carriers include Nextel and Boost Mobile.
Remove the back cover of your phone.
Look for the SIM card. If your phone works on a GSM or iDEN network and you do not see a SIM card, you must remove the battery to access it. Most devices have a notch cut into the battery so you can pull it from the back of the phone. Once you remove the battery, set it aside.
Gently pull the SIM card from its slot in the phone. Usually, you can remove the card by placing even pressure on the exposed part of the card and pulling it from the device. However, SIM cards can be difficult to remove if they are left in a single device for a long time, in which case you should put some pressure on the card using a pencil eraser or similar object.
Remove the back cover of the device in which you want to insert the SIM card.
Remove the battery from the phone, if necessary, using the process outline in Section 1.
Remove the current SIM card from the phone and set it aside. Be careful to avoid touching the SIM card connector, as this can damage the SIM card. The connector is the metal strip on the bottom of the card, located where the card makes contact with the phone.
Push the SIM card from Section 1 into the phone. Verify that it is inserted correctly; if the installation location is not obvious, look for a diagram sticker, near the SIM card slot.
Insert the SIM removed in Section 2 into the device from Section 1.
Reinsert the batteries on both phones and clip the back covers in place.
Power on both phones. Verify that the phones connect properly and that you have voice and data services.
SIM cards can only be swapped between phones if they are branded by the same carrier or sold unlocked, which is often the case on devices imported from Europe. For example, a T-Mobile SIM card will not function properly in an AT&T device unless it is unlocked, which carrier-branded devices are not by default. However, a truly unlocked GSM device can function with any SIM card, as long as the SIM card has service and the carrier being used is supported by the radios installed on the GSM phone.