Ibm notice period issue

I resigned recently and proposed date of 30days. I know that it's officially 90days. So i talked to my manager. He said he Will get back to me. I again send a reminder mail to check into this. Without replying to that mail, they rejected my proposed dqte and approved fo 90days What to do now? I am actually in active project from 2years and it extended for another 6months . They didn't even consider my extra leaves and buy out. What options do i have