Once you’ve activated your iPhone with your carrier, it should continue to work on the cellular network without any problems as long as you’re within range of a tower. Nevertheless, the vagaries of ...

What is a SIM card used for? A SIM card, or a subscriber identity module/subscriber identification module, is a tiny memory card that contains unique information and is linked to a particular network ...

After you purchase and use your cellphone for an extended period of time, you can change networks. However, the phone that you're currently using may not be offered on that network. If you wish to ...

If you’ve bought an iPad with 4G/cellular capabilities (we discuss whether that’s a good idea in our 2015 iPad buying guide) or a new iPhone, you need to buy and install a SIM card. Here, we explain ...

If you can't make a call or if you see an error message that your phone's SIM card is not working, there are several ways to troubleshoot the problem. Ther error ...