Company Forcing Me To Serve 90 Days Of Notice Period

Company Forcing Me To Serve 90 Days Of Notice Period. Hello, I work in an IT service company in Pune, Maharashtra which I joined on 1st Nov 2021. In my offer letter notice period is mentioned as 60 days. 1 month after joining the company, management decided to change the notice period to 90 days as a company policy for each employee. But during that, they asked for our consent which I did not give. I have it in an email as well from an HR help desk that I'll have to serve 60 days of the notice period. But still, when I want to resign they're asking me to serve 90 days of the notice period. I talked to HR about this and they said each employee was contacted personally by HR and was given an option either agree to the policy change or resign within a week. Now the problem is there is written communication about this in my inbox from my HR or even an informal message on a company messaging application. I want to know if it's legal and if can they force me to do it even if my offer letter says 60 days of the notice period.