The phone's audible ringer can be switched off. Unlike disabling the ringer, this only affects the ring and does not affect the visual alerting.
1.Press the 
button.
1.Use the up and down cursor keys to highlight Call Settings. Press Select.
2.Use the up and down cursor keys to highlight Audible Alerting. Press Select.
3.Use the left and right cursor keys to change the setting.
4.When completed, press the Save soft key.
5.Press the Exit soft key to exit the menus.