How do I get my full and final settlement?

Hi Sir, I joined in a small recruitment firm on 18th of December 2015 , in my offer letter they have only mentioned my designation my gross CTC and date of joining . No other employment clauses are there like the notice period , leave policy , working hours or even shift timing . After joining January 2016 they deducted 2500 and February 2016 they deduct 12500 and on 24th March 2016 they told me that management have some issue with me so my hr asked my resignation , so I put my paper and they accepted and on that day only I got my relieving letter and service certificate. Till now I have not got my payslips for January, February and March withe the salary for March 2016 along the deducted amount for January February 2016. Am continuously chasing them, I visited their office they are giving me 12350/- in post dated cheque dated August 2016, I asked about the deducted amount they said that I was marked as late in January February and March 2016 . So I didn't take the cheque and dropped 3 e- mails to that hr manager but they are still not responding . Its almost 2months I still have not received my dues with my Form-16, my payslips and my dues. They said its company policy that they clear FnF after 90days, but no where its mentioned in my offer letter . Now am from West Bengal , Kolkata and without those documents am unable to join some other company and its literally harrasment that I am chasing for my dues and papers which I rightfully earned and they are playing with me. Sir can you share any idea how can I get my dues along with paper from them. Abhishek Bakshi 9804509450