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 two ways of connecting your phone to a cellular network are very different. We tell you about each and how you can switch from one to another.

The rogue cellular network spanned '100,000 SIM cards across multiple sites,' and was used to make fake calls to US officials, including swatting threats.

If your new phone no longer supports SIM cards, or you don't want to use them anymore, you can convert to eSIM instead.