Unlocked cell phone information
A GSM phone is the one that uses the GSM technology (Global System for Mobile Communications). This technology is the most widely spread cell phone communication technology in the world. In the US, ATT and T-Mobile work on GSM, Verizon and Sprint, don't. You can check if you have a GSM phone by removing the battery, if you see a slot with a card in it like this then you are in luck. Once you know your phone is a GSM one, you need to know if it's locked or unlocked. Locked or unlocked refers to your phone's ability to work with any SIM card is inserted. Usually phone companies LOCK their cellphones so you can only use their SIM cards and therefore, pay only them for your communication. The easiest way to verify this is to have somebody else's sim card inserted on your phone (an ATT card in your T-Mobile phone or viceversa): if it's locked, it will say something like "invalid sim" or "SIM card registration failed" basically it won't work. If it's locked, most phones can be unlocked by companies that charge you anything from $5 to $50 to unlock them, either remotely (you can do it online) or physically (you need to take your phone to them). Search online for terms like "cell phone unlock" "unlock cell phone" and similar and you should see plenty of them. If your phone is unlocked or you get it unlocked, then you can rent just our SIM card to use on your trip overseas. Make sure to see the other requirements your phone must meet to work!