High jitter and constant "service interrupted" on account dashboard

I've been having the same problem in Las Vegas. I'm paying for both Gigablast and the $50 unlimited data plan (which really isn't unlimited by the way - it still throttles your speed when you reach your data limit - the limit is just higher) and I've been having the same random spikes in lag as well as disconnects. It affects everything I'm doing on the Internet. Streaming movies will suddenly say I've lost my Internet connection and the connection doesn't come back for 5-10 minutes. Large downloads have been interrupted. Web site pages won't load. All of my Amazon Echo devices complain that they have no Internet connection. When I check my Cox status, it always says "Service Interrupted." I've checked equipment, cables, configurations. I've reset modem, routers, switches, and client devices. I've used network test equipment and software on my local network. I've used an Ethernet cable tester on all of the cabling in my walls. The elimination of all possible on site causes indicates a problem in the Cox system, whether it's their demarcation cabling to my home, a damaged underground cable, or a faulty switch in their data centers. They need to do as much thorough testing on their equipment and cabling as I did on mine.