To set a PIN for unlocking, please go to the web interface for your end device and enter your personal PIN under:
Settings Preferences Keypad Lock
There, you can also change or deactivate your PIN.
You have the option to protect your telephone from improper use by locking its keypad. I.e. with the keypad locked, no outgoing calls can be dialed. However, the keypad lock can be deactivated at any time.