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 Management"
Click PIN Management.
Click the drop down list next to "PIN operation".
Click the field next to "PIN code:" and key in your current PIN.
Click the field next to "New PIN:" and key in a new four-digit PIN.
Click the field next to "Confirm PIN:" and key in the new PIN again.