Issue Resolved and full operations reinstated as of Friday, 10/26/18 at 5 pm.

UPDATE: While our telephone company continues to troubleshoot the root cause of the issue and told us at 9:30 tonight that it might be another full business day before they can resolve matters properly, a contractor we engaged was able to reinstate outbound call service at ~5 pm this afternoon with an interim solution that permits the placement of outbound calls for all of our affected phones. 
There is an issue with our telephone service that has left one of our two main communication channels not fully operational. As a result, while calls can be made TO all of our phones from those both inside and outside the district,  1/2 of our phones (numbers) cannot successfully place an outbound call. 

Our telephone company is aware of our outage and is working on service restoration — we have no estimate yet as to when they will finish.