Find "Phone password"
Press the Navigation key.
Scroll to Settings and press the Navigation key.
Scroll to Security settings and press the Navigation key.
Scroll to Change password and press the Navigation key.
Scroll to Phone password and press the Navigation key.
Change phone lock code
Key in the current phone lock code (default is 1234) and press the Navigation key.
Key in a new phone lock code and press the Navigation key.
Key in the new phone lock code again and press the Navigation key.
Exit
Press Disconnect to return to standby mode.