Extremely frustrated with Network congestion!

Every day between the time of 5pm-11pm my internet becomes completely unusable. I traded in my gateway for another new one already. Performing speed tests show I recieve between 0.00-350mbps of my 1200mbps connection with it constantly dropping to 0 every 2-3 seconds with the test simply erroring out at times. I call the xfinity number and can't speak to a representative. I use the mobile app and it says that I will be charged for a technician coming to my house to investigate a problem clearly on xfinity's end. If I can't resolve this issue by the weekend I'm bringing my equipment in and switching ISPs this is completely horrible customer service.