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 ...

Phone suddenly showing "No SIM" or "Invalid SIM"? Don't panic, there are a few quick checks that can get you reconnected fast.

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 ...

Activate your iPhone back to AT&T if the SIM card you insert after you install blackra1n onto the device doesn't work properly. Blackra1n is a third-party program that "jailbreaks" SIM-bearing iPhones ...

Switching or getting a New iPhone but want to keep everything you had before? For those who know it may be obvious but their are plenty of people that could miss that micro hole on the side as with ...