Customer service no help and have not been able to speak to a supervisor

One of our clients drop connection many times a day, which I have graphs from ping plotter to show this. Comcast says that the modem hasn't dropped a connection that it is perfectly fine. They came and replaced the drop. No help, still dropping so far three times that I know about today. I have called and asked for a supervisor to no avail, two different times. The first time the rep muted me until I hung up. The second time they "could not locate a supervisor". I used to work for Comcast and am pretty sure that something is wrong with the node, however Comcast has been denying all problems with this company. If there was any other provider beside DSL in this location, I would have had them switch by now. I also can not find an email address to try and get this addresses as well.