Your SIM card houses your phone number! In other words, your phone number is associated with a SIM card and not a device. This means that if you pulled an active SIM card (active line) out of an old Gabb phone and inserted it into the new one, the new phone would now have the same phone number as the last phone! This is because the SIM is associated with the SIM card and not the device itself. This is known as a SIM swap - in other words, transferring your phone number from one SIM card to another.