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 "Update SIM PIN"
Click SIM Security.
Click Update SIM PIN.
Click the field next to "Current SIM PIN" and key in your current PIN. The default PIN is 0000.
Click the field next to "New SIM PIN" and key in a new PIN.
Click the field next to "Verify SIM PIN" and key in the new PIN again.
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.