Who know OPS

hello everyone, i am a newcomer at an university in usa with an H1B visa. However, i was told I was an OPS employee when I want to buy medical insurance, then i have to pay all the money myself. It is expensive for me. I know nothing about OPS from my I-129 and 797B.Did the department cheat me? Can i change my status later? If i need not to pay tax for OPS?
If i could not change my status, if it means i can leave at any time in spite of two years's contract.
I know few about US laws, i wish I could get help from you. Sorry to bother you. welcome to contact me by email: [e-mail]