I am sorry to hear of your dilemma. I realize how frustrating this is for you and I hope to provide you information which is accurate and useful, even though it may not be the news you were hoping to get.
If you have no written employment agreement then you are, in all likelihood, an at-will employee. As such, you are pretty much subject to the whim of your employer. They can change your schedule, your compensation or even terminate you at any time and for any reason or no reason.
The only limitation is that the employer may not take adverse action against you in violation of your civil rights (unlawful discrimination) or out of sexual harassment.
If you believe your civil rights are being violated you can file a grievance with the EEOC at www.eeoc.gov.
Otherwise, it is really a matter of internal office politics or policy and not something which could be redressed in court.
I realize this is probably not the answer you were hoping to receive. Also, please remember that this is not necessarily a moral judgement on my part. As a professional, however, I am sometimes placed in the position of having to deliver news which is not favorable to a customer's legal position, but accurately reflects their position under the law. I hate it, but it happens and I only ask that you not penalize me with a bad or poor rating for having to deliver less than favorable news.