I am working in a company from may 2020. As per offer letter my notice period is 2 months or i need to pay the salary in lieu of notice period. But company has sent out a mail on 1st March 2021 increasing notice period to 3 months which unfortunately i have not seen. Now i got a job opportunity on June 14 and I put my resignation same day. I have informed my Manager through message tool used in my company that i need to be relieved by 25th July and i will pay for the due dates. Now my manager came to me and told me that He has not seen that message due to some problem in tool and it is not possible to relieve on 25th July so talk to your company and try to extend. I talked to my new company and told my Manager that i can serve till 8th August which is almost two months but now My current manager and HR are saying that they will not provide me relieving letter and try to take legal action.
What legal action I can take to get my relieving letter.