I think your talking about getting cut off while leaving a message in a mailbox right?
I would want to know what the caller hears, key voice always plays some prompt before dropping a call, the prompt could be your clue as to what the system thinks it's supposed to do. I've seen systems think they hear a DTMF digit when a person, usually a women, has a certain pitch to her voice. The Voy sys system had that issue. Also make sure these are not cellular callers.
mark

Reliable Telephone Service