I want to buy the notice period, but manger is not letting me buyout.

The below written in the inverted quotes is written in the offer letter, but my manager is not releasing me before 3 months. What should i do in such case, as i have to join the other company in a span of 45 days. "This employment can be terminated by either side, by giving one month’s notice during the probation period or three months’ notice after confirmation or basic salary in lieu of the notice period. Prior to leaving the Company, you will ensure that all your ongoing activities are successfully completed and properly handed over to the satisfaction of your manager/in charge/superior. However under no circumstances, the relieving period can be less than one (1) month from the date of acceptance of your resignation. The Company may also terminate your employment without notice and without any payment in lieu of the notice period in the event of breach of any Company policy or any misconduct. Without prejudice to the generality of the scope of the term ‘misconduct’ the acts of omission / commission as provided in Service Rules and as applicable in your case, shall be leveled against you: and your case shall be dealt with accordingly."