Full n Final Settlement- Relieving and Experience Letter not Provided by Employer

As per my Employer Appointment Letter, I was having 3 months notice period, so I asked my employer I will serve notice period of 1 month and will buyout the 2 months notice period as per the clause given in appointment letter. But my employer refused me to do that and said you only have to serve 3 months notice period and neglect the clause of appointment letter which I highlighted him, before resigning via mutual discussion. Even I have balance of 28 days Earned Leaves, 16 days salary and some overtimes. Also employer has balance towards me of Rs. 28000/- which was taken against salary. So, I have serve 1 month notice period and left the company and asked my previous employer to give me full and final settlement, relieving and experience letter by reminding them via mail for 10 months. After 10 months they replied to my mail and asked me to come for mutual discussion in their office for full and final settlement. I attend that discussion and then provide me partial full and final settlement which does not include my overtimes and no clarification on calculation, how they calculated. So again after this meeting I send them reminder mail for provide me detailed calculation with including overtimes. My previous employer is refusing me to pay for overtime, as I have provided him all my timesheet records of overtime. He is only agree to pay me for one of the project overtime and not for remaining. So, now I am continuously every month sending one reminder to my previous employer to provide me detailed calculation of full and final settlement, relieving and experience letter. It is now 14 months already completed, but my previous employer not providing anything from above. So Please advise me what should I do further.