Sudden Demotion, pay cut, and being told to take it or leave. Help?

I work for a Verizon call center where I am (was) a QA Auditor. Recently, I've been told that they no longer have "part time" so they will be demoting me to the sales floor (cold calls - which is where I started 2 years ago) and that I would have to take a pay cut.
They haven't given me work in almost a week even though I'm willing and able to work. On Monday, however, they called me in to attend a "Political Meeting" (whatever that means)
The thing is, I'm on disability and I'm only allowed (and able, healthwise) to work part time (max 5 hours a day). The company hired me knowing this and accepted my terms, if anything they were glad they couldn't pay me over a certain amount, now they're telling me to either take a demotion or leave... I want to know if this is legal? There is no policy in place, by the way, to show that the company doesn't want part time in my QA Auditor position, it's the new manager who they hired, that said he just doesn't want part time because he is wasting money. I have proof, to show otherwise, that I'm one of the most productive and best workers in that department so as you can understand I'm very angry about this sudden demotion. Any advice?