How do I get out of a work contract?

I am a NP and signed a contract with a medical group that has an Urgent care and office/hospital. During my interviews I told them I would work 3/12 hour days and I wanted to work in the ER. Various things happen such as no doctor would sign papers for me yo prescribe medications. never had my own computer, no training,etc. I submitted my 2 weeks notice, as everyone else did. The CEO called and said he wasn't accepting my resignation. When I can into work, my manager showed up and told me I would be working the 90 days, 6 days a week at Urgent Care, and took away my paid time off. Now I work M-F 4-9, and Saturday 9-4. Never the hours I agreed to or the place I agreed to work. What can I do to get out of this?