Refusing to accept resignation with 1 month notice - if I handle this situation legally what factors should I keep in mind?

I am working in a Ltd company and recently resigned on 01st August, 2018 and mentioned 01 month notice to relieve. As per my appointment letter if I get confirmation letter than only I am bound to serve 03 months notice period, if not than only 01 month. Its being 02 years and 02 months I have completed in company but didn't get any communication stating that I am a confirmed employee. Now my company's National Business Head to whom I was reporting refusing to accept resignation with 01 month notice and pushing me to serve 03 months notice.
I have to join other company in 01 month. Also, National Head is not taking my calls and not responding on emails. I am feeling irritated, harassed by their behavior. Also, if I don't join other company on time I will loose other job opportunity as well. Kindly help me and advise me to how to tackle this situation. Legally my appointment letter favors me and company can't hold me or put pressure on me to serve 03 months notice period. Also, in case if I go and join other company, I have to provide experience letter which my current company will not provide, as my current manager and National Business Head wants to mentally torture and exploit.
Kindly advise as if I want to handle this situation legally, can I proceed and what all factors should I keep in mind.
15th August 2018 From India, Noida

Attached Files (Download Requires Membership)

Notice.PNG (105.5 KB, 188 views)

Handling a matter legally when you have only one month to join another firm has a practical proble of time.Litigation takes time, while you may get justice eventually.
Some questions will arise?
How long was probation as per appointment order?
Did you ever remind them about completion of probation and confirmation order, though it is the company responsibility to issue orders.
Is your National head co located?
In which case go and meet him personally.
Expenditure on litigation will be there.
You will have to take a balanced decision and go for litigation weighing all factors like time delay, option of paying 2 moths salary and leaving (though you may not be legally wrong)
Best will be to consult a local advocate and take his opinion.
Is your establishment registered under State shops and Establishment Act?
15th August 2018 From India, Pune

If you are not confirm employee, there is no need notice period to serve, however you should follow the minimum notice period serve policy as per the appointment letter, if they forcefully say to serve 3 month notice, this will be unfair practice against the employee and law. You should request them and meet personally the unit head, hr head for the relieving letter. Any kind of letter is issue from HR department, after the resignation and acceptance of the resignation there is not a single role of your reporting manager or any superior boss you should ask to HR department, submit the no dues and get the relieve.
15th August 2018 From India, Meerut