I have had the same exact problem as you. Constant wifi disconnecting. Tech came out wires replaced, said could be noise in the lines that they would send a line guy out and to this day not sure if they ever did or not. I don't know how to determine all that stuff that was done above but for something that cost over $100 per month just for internet this is not right.
What do the modem's signal stats look like ?
Please post the *Downstream Power Level*, the *Upstream Power Level*, and the *SNR* (Signal to Noise Ratio) numbers.
Some tips for improving WiFi performance;
There are other options. Google for WiFi repeaters / range extenders, WiFi mesh systems / pods, powerline ethernet adapters, MoCA adapters.