How to reduce the 3-month notice period to one month upon resignation

Hi Sir/Madam.

I am working in a construction company. I gave a resignation letter to my company for one month notice.

But in my agreement (should either party desire to terminate the renewal contract, such party shall notify the other party of such desire within 3 months prior to the date of termination. Such period shall be similar for both parties.

Both parties have agreed that the termination wage to be paid by the terminating party to the other party shall be equivalent to the value of the worker total wage in 3 months. Such wage shall be similar for both parties.

But my present company informed me that I am not allowed to go now. I'm allowed to go only after the completion of 90 days.

Please can you give some suggestions on how can I be released from my current company?