Customers call and get a message that our phone has been disconnected and no longer in service

We just recently opened our cat hotel and are new to the Comcast Business services. During the first week of our Grand Opening our phone had an outage unrelated to the area. The customers were calling us and getting the message that the phone number is no longer in service and has been disconnected.

We called Comcast Support and they updated the software and claimed that the problem was resolved. The ticket CR65401868 was closed.

Today our clients called us and got the same message. They thought we are closed and drove to our competitors. 

The sad part is that unless we constanly call our line and check, we can't really tell when this is happening. 

The phone goes back on and off without us being able to notice when, and we are losing business over misleading message that the phone is no longer in service. 

Our Comcast Sales Rep stated that technology is never perfect. How can we fix it?