Blatant misclassification of employees, refusal of gratuity

After doing everything possible to plead with my former organisation internally to rectify their erroneous understanding (or) deliberate misclassification of employees for whatever reason, I am being responded with a veiled threat by having their lawyer send me a nasty email accusing me of trying to extort money from the company. Briefly, the issue is that the recruits who are hired initially as contract staff have been marked "independent contractors" in the appointment letters for years and rather than fixing that botched up system of hiring, the company has been doing patchwork to safeguard themselves from litigations by adding more points that enables them to circumvent the provisions of labour laws. When pointed out that being made to sign newer extension letters with subtexts that virtually instruct staff to forsake their fundamental right to social security does not make an employee ineligible to claim gratuity after resignation, there seems to be no one interested in paying heed and I am only being mocked at. This raises suspicion whether the organisation is doing this on purpose and is engaging in a very immature way of camouflaging themselves from the eyes of the law. I have worked for 9 years and 10 months in this organisation doing the role of a full-time employee and the company is blatantly denying me gratuity even though I had not agreed upon such a set up nor had I been compensated differently or any more than other employees performing my role and having a tenure equal to me. It is more than clear that every justification given by the company to deny me gratuity is completely illegal and their legal panel is also committing perjury by blatantly lying about something that they personally witness. This so-called lawyer has had direct or indirect interactions even with me while I was in service and his email looks as though he doesn't even know me or the role I was playing. Employees hired for full-time roles are being tagged "consultants" as though they are some medical or legal experts who just give advice to the company and can instruct the company to follow their suggestions; when that is not at all the case. Switching jobs is a very casual activity in corporate organisations and the only purpose for me having spent more time after the initial 3 years was with the hope that I am only adding to my gratuity and getting a better pay by switching to another organisation effectively does not give me extra monetary benefits on a long-term basis. However, the company seems to not want to care at all and is behaving like I was a nobody according to them (as per this legal team's letter) and they owe me nothing despite having been loyally associated with the company for over 10 years. It is pertinent to note that this company has a known history of hoodwinking the law by brining up some baseless and invalid clause they dig out from somewhere and file petitions in court and hence officers can't penalise while the case is subjudice