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
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.
It costs many thousands of dollars to bring a lawsuit in the US, and you will almost certainly lose against a huge corporation with their own legal team. They can simply outspend you until you give up.
Not if the amounts are small enough for small claims court. The laws vary state by state but here in California, the max for small claims is $10,000 and the company can’t just hire a legal firm to defend it, they have to send a corporate representative. They can send a lawyer if they have general counsel employed by the company, but few companies are big enough to have that and those that are generally won’t send them out for small claims. Many times they won’t bother at all and it results in a default judgement.
The filling fees are in the hundreds of dollars and the judge are used to working with the general public as opposed to well represented plaintiffs with expensive lawyers.
You can often take telcos to small claims for the few dozens or hundreds they owe you, and they won't bother to show up. You'll get a default judgement for the cost of court filing (varies, $20-$100 usually). If they don't pay, you bring the sherrif to one of their offices to start dragging out an equivalent resale value of equipment unless somebody writes a check in ahurry.
The GP already lost 6 days of work… how much would the likely payoff be to make it work their while to continue dealing with that company?