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.

These are the best Amazon Fire tablet deals for October 2025, with the best prices for Amazon Fire 10, Fire Max 11 and Fire Kids models.

These are the best Android phones available right now — powerful, stylish, and packed with AI features. Find your next smartphone today.