marketforce Refused payment for services performed. east greenbush, New York

I have really had no problem with this company until January 2011.  This company sends out Mystery Shoppers as well as Movie Theatre Auditors.  I was asked to perform a job in late January, but I could not complete it.  They claimed that since I did not "complete" my task, I would not be paid.
I had done blind checks before, and I understood that it is imperative not to get caught by theatre personnel.  So after that incident, I told the company that I would do no more blind checks for them.  They offered me open checks instead. 
I had done numerous open checks for them before, but this was done in late July.  It is now September, and I am still waiting for payment.  They say allow 4-6 weeks for payment (which is inefficient to begin with), but it has been 8 weeks now.
I can not call anyone to voice my complaint, and my emails go unanswered.  This company requires a hard copy of every job that is completed.  I send that in every time.  I also fill out online paperwork on the company's website before sending in my hardcopy.
Marketforce asks that the hardcopy reach them 3-5 days after being mailed.  I have no control of when it reaches New York if I am mailing from Arizona.  Plus, I always mail the paperwork the Monday after the task is done.
I am so tired of being promised something that is never delivered.  Too many people are looking for work, and companies that take advantage of people like this need to be stopped.