I was having the same problem over a couple of months. Internet service would come and go. After numerous frustrating phone calls and 4 different visits from technicians, they finally sent someone who checked the connection at the pole. Turned out that squirrels had chewed through the wire and was “shorting” out. Guy spliced in a new section of cable and everything was fine. Don’t know if you have squirrels running across your lines but if so someone should check for damage.