Unlawful demotion? I feel i am being discriminated against, and demoted unfairly.

I am a 2 year employee at a bank and have always risen far above what is expected of me at my position. Have always recieved exemplary evaluations, thus recieving several promotions. My fulltime position allows me the benefits of health insurance, paid vacations, etc... I am also a student in college, and after the previous semester i had some scheduling issues, but nothing that could not be worked around, and nothing that would cause me not to be able to put in my full time hours. I spoke with my manager of these scheduling issues and she agreed that they could be worked around. This was three months ago, so of course i went ahead and planned my next semester based on this agreement, and thinking that i could keep my fulltime status. To make a long story short, now that i have got my school schedule lined out, they are demoting me, and of course i am losing all of my benefits because of this. I had ample amount of time to make other arrangements if they would have been up front with me, and i am just wondering if there is a case for me being wronfully demoted?