FCC can be surprisingly effective. My friend had a problem with his ISP randomly dropping routes to some of the ASs, and the support was useless, because all the speed test sites were fine

An FCC complaint got that fixed in two weeks.

An additional option to consider is to file a complaint with the Better Business Bureau.

I had an issue with my wireless carrier repeatedly refusing to issue credit for a months-long ongoing problem on their end.

Within 2 days in filing a BBB complaint, I had a rep from the company asking how much I thought seemed fair and if I wanted a bill credit or a check.

You can't buy the satisfaction that comes from forcing the phone company to do what you require.

When Comcast tried to screw me out of $700 the FCC solved it for me pretty quick. I'd at least recommend giving them a try even if in the end they may not help.