If you were smart about business, you would be figuring out how to make more money, not how to get even.
There is no justice in the world, shed yourself of that childish naivety. Sometimes you just get shit on. The question is whether you want to keep rolling around in shit, or you want to clean yourself off.
This. We recently got into a dispute with an ex-landlord over how much rent we owed/didn't owe him. Basically he breached our tenancy agreement in a big way, then claimed we still owed money. We took legal advice which told us he was 100% in the wrong, and had done stuff which was actually a criminal offence (not just breach of contract). Had we gone to court, we would have won. But I still settled with him. Why? Because I've learned that fighting over money - or anything - is very rarely worthwhile, and represents a scarcity mindset.
It's far more profitable to focus on making money, and since settling I've landed 4 new clients who will be worth at least 20-30x the amount we were disputing.
By continuing to chase this, you are like an investor who pumps money into a company which is clearly fucked, just because of "what you've already put in." You're giving these guys your time, energy and attention, all of which are FAR more valuable than your money.