Department not giving me TAships?

I got in a dispute with a professor I TA'd for, and now my department is not giving me TAships. What should I do? I am required to teach more classes in my department in order to satisfy a graduation requirement. In addition I do not have research funding and I'm dependent on TAships to make money.

Nobody actually told me I wouldn't be allowed to TA again, but I suspect I have been blackballed by my department (and there's no way for me to know, since the application process is opaque, and they can just keep rejecting my applications without telling me why).