Is there a way to turn off the ringer temporaily on a 2616 non display phone? The user often has a cell phone in progress and doesn't want to hear the incoming ringing on his 2616. I tried to turn the ringer down on the phone but it will not let me turn it off completely. Should I program a DND button on this phone so it doesn't ring or is there something in CLS or FTR that will allow him to silence the ringer with the volume bar?