Im ready to pay for notice period but my employer forcing me to serve notice period

I have submitted my resignation to my employer as I got a new job, we were having 2 month notice policy and which they changed it 3 month with the below clause. Dur to our endeavour to match best of the global IT practices, this is to inform you of certain changes the management has felt it necessary to introduce into the current policy structure. We hope that all our employees will read and correctly comprehend our new policy. The policy norms have been incorporated in the latest version (1.1 ) of the “Employee Handbook”. Here are some new changes: 1. The notice serving period for 90 days (3 months) in written or if unable to serve then pay three months gross salary in lieu thereof. 2. Return all the company properties or assets that are with employee and custody at the end of this period. I'm ready to serve 1 month notice period and willing to pay a 2-month salary to them but they are refusing it stating that we don't have a buyout option for NP and will only relive you once we get your replacement. can you please guide me on this, what legal option I have in this case?