Let’s say you spent your vacation abroad a couple of years ago. Being thrifty, you removed your U.S. SIM card from your unlocked iPhone 4 and inserted a SIM card from a carrier in the country you were ...

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 ...

The subscriber identity module -- SIM -- contains the information used to connect to your wireless carrier's network from your iPhone 4. If you are planning to resell your company's iPhones, you ...

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 ...