Don't know that I have advice for your current situation, but in the future I would say get contract copies if you can prior to starting. If you're writing your own contracts for what you're doing, there are lawyers and legal professionals who can assist in looking over to make sure its following laws and there's no loop holes.

I've worked with a few companies or organizations on a commission-basis with just a "verbal agreement" and it often results in either not getting compensated what I should have been (if at all), or takes quite a while to get what they owed (and it's sometimes still short). I don't know that it's purposeful or not, but it's hard to take further action without something concrete (contract) I've found, at least.

I tend to avoid these situations now unless I really need the additional funds. I've had a few that were no issues at all, but I'm much less trustful myself.

An unfortunate experience, for sure. I'm sorry that you've been experiencing this and hope that you are able to get it sorted out. Best to be professional as you can, though-- best of luck!