Actually the best suggestion here was to sell your work to someone else. You should tell the people that have "stolen" your work that since they are not going to pay you that you have found a buyer and that they will pursue legal action if they don't remove what is going to be their material. It might give them something to think about. If you threaten to kill the value of that content it just might get them to pay up. You have nothing to lose by this tactic. They can't sue you...it's your stuff that they have refused to pay you for. I say sell the material and/or place it somewhere like article city..kill the value of what you did. It should piss them off at the very least. I would be really mad if I was you and they got good rankings and such from the work.
Well, there's nothing preventing you from telling your story in public. Write your story and publish it on the web. Be purely factual, as if it were a newspaper article. Name these people and use your SEO skills to ensure the the page ends up at the top of the search engines when anyone searches for these people by name. If that doesn't get their attention, then at least people doing business with these two in the future will have fair warning. I tend to Google people by name before I get into a serious transaction with them.