Full & Final settlement after resignation

I was a permanent employee of a ltd. company (registered in delhi) from Sept 2013 to June 2017. On 10th May 2017 I resigned from my position and served a complete 30days of notice as per the employment agreement of the company. I completed all the formalities of work handover and clearances from departments on my last day and got relieving letter from the company. Now even after 2 months I am yet to receive my Full & Final dues. The HR, Managers etc are not picking up my calls, nor replying to my various emails. This company is into construction business and has a vast history of cheap tricks like delaying salaries, holding payments of employees, suppliers, subcontractors etc. Also they have defaulted in crediting the TDS of employees to Govt and have not issued form 16 to all the employees since FY 2013-14. Due to this, I am also not able to file income tax returns and avail any housing/car/personal loan from banks/pvt firms since last 3 years. I had already sent several demand notices on mails and also I have sent a legal notice recently to them but didn't respond it (as expected). I need to know what is the next step to be taken, do I file a case or complaint? what is an average time for such a case to solve for settlement? I have all the supporting documents including attendance record, salary sheets, handover documents, relieveing letter, bank statements etc. Pls help.