Does anyone know why "Group Call" would appear on a DT330 display? Two phones on our sv8100 system were beeping the other day for about 10 minutes and had the message "Group Call Line 033" on their displays. The only additional information I can give is that the beep tone was similar to a confirmation tone. And you could still call out with the phone, but as soon as it was hung up, the beeping continued and message remained. Thanks for any suggestions!