Set a screen lock on your phone and a PIN for the SIM card

Cost: No cost at all. You only need to set the screen lock and the SIM PIN once each.
In plain terms: The SIM card is that tiny card inside your phone that receives SMS verification codes. If your phone gets lost, a finder can remove the card and insert it into another phone to receive those codes, then reset all your accounts one by one. Setting a PIN on the SIM card means that whenever the card is moved to another phone, the user must enter that PIN before the phone can be used — effectively blocking that path.
Benefit: Without a SIM PIN, a finder can easily move your SIM card to another phone, receive verification codes, and reset all your accounts. With a PIN in place, that entire process is prevented, keeping your accounts safe even if your phone is lost.
Evidence grade: C
Sources:作者经验，无直接文献
Notes: You can set the SIM PIN under “SIM card lock” in your phone settings. The default factory codes are usually 1234 or 0000. If you enter the wrong code three times in a row, you’ll need the PUK code provided by your carrier to unlock it. After setting the PIN, be sure to write it down somewhere safe.