You may be able to use the Features menu to switch 'forward on no answer' and 'forward on busy' on or off.

1.Press the Features soft key if shown. To do this during a call, press the key phone PHONE key and then press the Features soft key.
2.Use the up arrow up and down down arrow arrow keys to highlight Forward. Press Select.
3.Use the up arrow up and down down arrow arrow keys to highlight Fwd Busy/No Answer. Press Select.
Use the up arrow up and down down arrow arrow keys to scroll through the menu options.
To switch 'forward on busy' on or off, highlight Fwd Busy and press On or Off.
To switch 'forward on no answer' on or off, highlight Fwd No Answer and press On or Off.
To select which calls are forwarded highlight Call Type. Press Change to change the option between All Calls or External Calls Only.
To change the destination highlight Destination and press Edit. Enter the number and press Select.
Press Save to save any changes.

Access Control

Your system administrator can configure whether you can access this menu option. See Menu Access Control.