Is this legal? Do I have a case?? Can I sue?

maybe you have some type of prevailing wages case where you should be paid in accordance with the going rate for the work which you are performing. I know this works in different situations, but you might want to look more into it. Also, if you know in advance of conversations regarding increase in pay in exchange for certain work you should perhaps record the conversation as long as you are directly involved in the conversation (otherwise it could be deemed inadmissible and potentially criminal in some states). I would research for cases in both federal and state court dealing with workers' rights and wages as well as job titles and how wages are set. You could also check state and federal workers' comp claims before administrative judges and see if you find anything there to help. But it sounds like you have something I just don't mess with employment law too much at least in this regard. good luck and stick it to them as they have you.