If you are new to Samsung Galaxy devices and you have no idea how about the proper way to disconnect or add a SIM card, this brief tutorial should help. How to insert SIM card on Galaxy Note10+ ...

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.

SIM cards link accounts to handsets. They keep communications private. They store messages. Although small and simple, they are a big part of modern mobile phone systems.

Note that the iPad requires a micro-SIM card. You can cut a full-size SIM down to micro-SIM size using a specialist tool or household cutting equipment but proceed at your own risk (see Resources).

Activating a new SIM card on your iPhone is a simple process that just takes a few easy steps. Read more: Best iPhone of 2024 Follow our step-by-step guide to help get your new iPhone up and running.

An easy way to make sure you can switch out SIM cards quickly—as soon as you land stateside, for example—is to carry a paperclip on your keychain or clipped to your wallet.

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.