A SIM card, or subscriber identity module, is a small card in your cellphone that lets you place phone calls, send text messages, and more.

These two ways of connecting your phone to a cellular network are very different. We tell you about each and how you can switch from one to another.

A SIM card, or subscriber identity module card, is essential component of any phone. It connects your device to a cellular network and stores vital information, including your phone number. Many ...