when we place a call on hold the phone lets us know they are on hold, this is a great feature, however sometimes we need to have people on hold for long periods of time and the phone calls us back with a parked call message every 20 seconds, this is very frustrating, as we can be on the phone to whoesalers for up to an hour, and must keep picking up the phone, I need to know how to lengthen the time between placing a call on hold and it calling back to remind me someone is there. PLEASE HELP!