Mobile phones that use Global System for Mobile Communications (GSM) technology store the phone’s user and carrier information on a Subscriber Identity Module (SIM) card. Some phones come with dual SIM slots, allowing users to install and use two SIM cards at once. Most cell phones, however, only have one SIM card slot, meaning that only one SIM card can be installed at a time. Nevertheless, if a single SIM cell phone user has two SIM cards from either the same or different carriers, it is possible for her to use them interchangeably. Writer Bio
