Having major echo problems on a 6.0 so we upgraded to 7.0 to see if problem clears. (It did not) Also running all 9620 sets. Tried installing a 5610 just to see if the phone model made a difference. But after installing the extension number comes up but no buttons are programmed (Manager says there are)and cannot use phone. System status says classmark unknown under phone type. Manager says other phone type. Cannot find this error in google. Anyone come across it before?