You can lock the use of your SIM with a PIN. If you activate it your SIM PIN, you will have to enter the PIN to make phone calls and use data.
The SIM PIN is a 4 digit code. You can change your SIM PIN in your phone settings if you would like to make it something more memorable.
Also, it means that if your phone is lost or stolen, your SIM PIN means no one can use your SIM card.
Each time you switch your phone on, you’ll be asked to tap in your PIN and off you go.