Hi I have a uc520 phone system with 3 shared extensions. When callers call any pstn lines they are forwarded to extenion 1 if busy it calls extension 2 and extension 3 is setup for vmail when no one can answer. My problem is that if you are on line 1 and someone calls it beeps like call waiting and if noone answers the beep it goes to line 3 vmail. You have to occupy 2 calls on the same extension in order for call busy forward to be present.I want to change the line so it doesnt have call waiting and when someone is occupying it, it will goto line 2. The extension needs to be configured as a single line not dual. How do i do this?