Your PIN protects your SIM from unauthorised use if your mobile phone should get stolen. You can change your PIN to a PIN of your own choice making it easier to remember. Before you can change your PIN, you need to turn on use of PIN.
Tap Security & privacy.
Tap Set up SIM card lock.
Tap Change SIM PIN1.
Key in your current PIN and tap OK. The default PIN is 0000.
Key in a new four-digit PIN and tap OK.
Key in the new PIN again and tap OK.
If an incorrect PIN is entered three times in a row, your SIM will be blocked. To unblock your SIM, you'll need to key in your PUK. The PUK can be obtained by contacting Customer Service. Please note: If an incorrect PUK is entered ten times in a row, your SIM is blocked permanently. In this case, you'll need a new SIM from Optus.