Employer not accepting my resignation even I am serving notice period

Hi Advisor, I request to Advice on my issue. Am working as consultant since last 2.5yrs. I am in New service agreement from 01.01.2021 to 30.06.2022 i.e. 1.5yrs. In which it is clearly mentioned that if i resign before agreement expire then I am liable to pay monthly bonus which took from agreement start date to resign date & additional 50K as breach of contract. In June 21 I got a call from one of MNC Company for recruitment, so I applied & luckyly cracked the interview & I offered approx 90-95% hike. With this opportunity I send my resignation to my employer by stating that I am ready to buy off service agreement with serving 3 months notice period even though my employer not accepting my resignation. I expect he don't want me go for better opportunity because I signed in service agreement. He rejected my resignation by stating your resignation has rejected by management discretion power. I request to suggest solution to my problem as I have some my personal life goals it will begin to fulfill once I step into MNC.