Internet Speed Issues

I have been having issues with my internet for many years now. This year alone I have had nothing but problem after problem with the speeds dropping to below 10mbps. I'm on my 3rd modem and called numerous times to try and get a tech out to fix my problem. Most of the time the problem occurs around 8:00PM. But, it has also slowed down all day. When a tech does show up the speeds are always back to normal and I explain to the call center person that the problem is at night, when a tech is not available, and it would require a monitor or recorder on my system to capture the problem. Most times that I call when the speeds are slow the call tech can't see my modem online. I have had techs come out and see a problem and they turn in a work order to the maintenance crew only to have the maintenance crew cancel the work order because they didn't see a problem. I have been told a maintenance crew was coming out to check the problem I waited all day for them only to find out they cancelled the work order. I have been trying to talk to someone higher up than a field tech for years now to no avail. This is totally unacceptable service for the price I pay for the lousy service I am getting.