A Subscriber Identity Module, known as a SIM card, is a programmed microchip that is placed inside a Global System for Mobile Communication (GSM) mobile device called a cell phone. The SIM card identifies the user to the mobile network that the user subscribes to. Therefore, if you don't have a SIM card, you will be unable to use your phone [source: ATT]. There are various reasons you may want to replace, or move, a SIM card. SIM cards can be switched from one phone to another. If you buy a new phone or borrow a phone temporarily, and you want to keep your old number and the same provider, all you have to do is take the SIM card out of your old phone and insert it into the new one [source: Computing]. We will now show you how to replace a SIM card on your Samsung Galaxy 5.

  1. Locate the notch on the bottom edge of the back panel of the phone.
  2. Lift the back cover by using the notch located above.
  3. Take the battery out of its compartment.
  4. Slide the SIM card out of its slot.
  5. Align the new SIM card so that the gold contacts are face down and the notched ends are closest to the battery contacts inside the phone.
  6. Slide the SIM card into the SIM card slot.
  7. Match up the gold contacts on the battery with those inside the phone.
  8. Place the battery into position.
  9. Replace the back cover, making sure it snaps it into place [source: T-Mobile].