AT&T and other cellular providers using Global System for Mobile Communications, or GSM, technology install SIM cards in their customers’ mobile phones to identify each device to the network. If you want to take your AT&T Android phone to Europe or Canada and use a world plan there, you can do so, but first you will have to unlock the phone for use outside of the AT&T network. Otherwise, the phone won’t be able to accept another carrier’s SIM card. If you just use your phone without subscribing to a plan on the carrier’s network, you may incur much higher charges. Tips Warnings Writer Bio
