As an alternate to call timer display, you can have the phone briefly (4 seconds) display the duration of the call after it is ended.
1.Press the Features soft key if shown. To do this during a call, press the PHONE key and then press the Features soft key.
2.Use the up and down cursor keys to highlight Call Settings. Press Select.
3.Use the up and down cursor keys to highlight Show Last Call Duration.
4.Press Change to change the setting between On or Off.
5.Press the Save soft key.