The PIN protects your SIM from unauthorised use if your router 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.
Find "PIN Code Management"
Click PIN Code Management.
Click the field next to "Modify PIN Code".
Click the field next to "PIN Code" and key in your current PIN. The default PIN is 0000.
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.
Click the field next to "New PIN" and key in a new PIN.
Click the field next to "Confirm PIN" and key in the new PIN again.