Phones Keep Dropping In and Out

Hello all,
At my job we support a client that is having phone issues and have had them for a while. I was going through the logs today as its getting intense and after resetting everything on the network it still did not help. I found some errors that keep happening and I googled these error but could not find a real answer as to why these errors are happening or what can cause these to happen and if they are related to the packets being dropped at all. I just noticed I can not post a screen shot so the following error is…

ERROR[3536] tcptls.c: unable to connect STP socket to Connection refused.

This error happens many times randomly in the logs. We might be handing over out phone support to another business for this client because we can not find out why there calls go in and out so many times. Today it got to the point where I couldnt even have a conversation with them. So any help is highly appreciated! You have no idea lol