Find "Change password"
Press Menu.
Scroll to Settings and press OK.
Scroll to Applications and press OK.
Scroll to Call and press OK.
Scroll to Voice calls and press OK.
Scroll to Call barring and press OK.
Press Options.
Scroll to Change password and press OK.
Change barring password
Key in your current barring password (default is 0000) and press OK.
Key in the required barring password and press OK.
Key in the barring password again and press OK.
Exit
Press Disconnect to return to standby mode.