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.

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.

Managing Editor Josh Goldman is a laptop expert and has been writing about and reviewing them since built-in Wi-Fi was an optional feature. He also covers almost anything connected to a PC, including ...