Absolute worse nightmare you can get from an ISP

We were promised fiber, our fiber had 2 400-600 downtimes a day, two minutes at a time... after 3 months of begging them to fix it, trying to be patient, liaising, sending them helpful videos of the problem over and over again, contacting dozens of their staff, we switched over to a different provider, now they're persuing 5 months worth of payments or internet that didn't work on day 1.