What is Personal Unlocking Key Code (PUK)?
An 8-digit number known as a PUK code (or simply "PUK") is used to activate a protected SIM device. Similar to a "password refresh," it restores the SIM card Passcode and gives you the option to select a new one.
It is a good idea to have a backup plan in case the backup plan is not successful. If you are unable to locate the PUK number, your cellular provider might be able to help.
SIM Card PIN
The SIM card cannot be used without the 4-digit Password. When you initiate a new phone, put in a new SIM card, or move a SIM card to another phone, you might have to input the Password. Your smartphone may ask you to input the Password each time you turn it on, depending on its options. In most cases, changing the Password on a mobile device involves heading to Security SIM Security in the options menu.
After three unsuccessful attempts with your Password, you must input the proper PUK to open the card. The SIM card will become forever disabled and you will need to replace it if you input the incorrect PUK number ten times.