I'm looking for open discussions with theatre owners operating between 2 and 6 separate locations interested in improving voice communications between sites while reducing monthly and annual charges by 50% or more.

What are your challenges? Costs? Availability of Announcement Voicemail Service? Handling multiple calls? Busy lines?

Yes I was looking into this. There are many VIOP options out there that can help do this. I ended up with the local phone company's answer only voice mail system. It was pretty cheap and I did not need all the features of the auto attendant. Also a lot of those VIOP systems will let you leave a long message but only a 60 outgoing message.