You have mentioned in your post that:
-GM fired you. Did the company issue any termination letter to you?
Or you have submitted resignation letter/notice of resignation?
-You have sent filled in clearance certificate.
Have you obtained any acknowledgment, and subsequently NOC.
- GM has restricted you from entering the office.
Has he issued any written communication, and have you received any copy?
-GM has stated to you that your relieving letter and settlement of dues shall be cleared by HR.
You have mentioned that you have written to HR but HR is neither responding to your emails or phone calls, and you are restricted from entering office.
-You have joined services with another company.
It seems that no attempt was made by either party to reconcile the matter.
Did HR call you for any enquiry or meeting after the incidence of arguments, or firing, and did they issue any letter/show cause notice etc to you? Hope you were right in your explanation to the technical matter over which you faced heated arguments.
You should submit a written representation to your appointing authority, MD, Company Secretary, and you may explain all events in chronological order, date wise, and demand your F&F, work experience certificate, relieving letter, form 16,PF accumulation reports, PF transfer/withdrawal forms, NOC/NDC-clearance certificate etc, settlement of dues to be supplied to you with in 15 days. It is important to represent since you are not getting any response and company might have declared you absconding.
You have the option of explaining the matter and submit your version. You should be able to furnish proof/valid reasons.
Company has to supply you work experience certificate, NOC/NDC, and may sit on relieving letter.
Please consult elders in the family, experienced and competent well wishers, and your lawyer/law firm and seek their help to draft your representation carefully. Based on facts, valid reasons, you can protest and contest your firing also.
If the company does not respond, you can lodge a complaint with the local of Labor commissioner.