Request for Early Release Due to New Employment Opportunity

I have been on the bench for a long time and currently do not have any active project work or project-related responsibilities. I have received an offer from another company, and they have provided September 15 as my date of joining. I have requested my current company to consider an early release, but they are insisting that I complete the full 90-day notice period. I also specifically requested the option of a notice-period buyout, but I was informed that there is no such policy available in the organization. Given that I am currently on the bench without any project responsibilities, I would sincerely request management to reconsider my situation and provide me with an early release. This situation is also causing me significant mental anxiety and stress, especially because I have a committed joining date with the new organization. I would really appreciate your support and consideration in helping me resolve this situation.