My Department Chief is not accepting my resignation from Company. What can I do to leave ?

I have worked in a reputed private company for almost 2.5 years. Due to the veiled workplace hostility and heavy nature of work (24/7 attention required in workplace - even when away from office or on leave), I have recently put in my resignation through the offboarding portal of the company. This requires 1st Level approval by Department Chief before HR can process the same. My Department Chief is not willing to let me resign and has returned the application. He wants to discuss this face to face again and is offering other options within the same department but simply not letting me resign peacefully. I am not looking forward to working in this sector again and do not wish to remain. The resignation policy requires either a 90 days notice period or paying of compensation for the shortfall period (i.e. if I give notice period of 1 day, I need to pay compensation of 89 days to the company which is equal to basic pay of 89 days). I do not wish to serve the 90 days period but willing to pay the compensation and had proceeded accordingly. But now I am in a roadblock where I have to apply again which will probably be rejected again. What can I do in this situation ?