Annual Incentives not paid by company after resignation

Hello, I worked for an Engineering Service Industry for about 3.5 years. When I resigned, I paid all the money as mentioned in my bond & got my experience/service letter & my fnf was done without annual incentives. At that time HR told me that you will get incentives once it is declared for all employees by management. When incentives for all employees was released they told me that my performance rating for that financial year did not make me eligible for annual incentives. Annual incentives are for financial year from Apr16 to Mar17. I would like to share few points because of which I think that I should get annual incentives, 1). I got promotion on 4th Aug’16 with a good increment in my salary. 2). I was sent to USA for onsite opportunity (from 12th Nov’16 to 30th May’17) where client was very happy & satisfied with my work. 3). When I resigned, my manager tried his best to match my salary expectations (new offer) but unfortunately management refused to do so & I was released with proper handover & fnf. Now, my question is why will company do so many things for a non-performing candidate..?? When was my performance poor..?? I also asked my company to share USA client’s feedback but they did not do that. Also, as per standard rules, company should inform me or warn me during performance review or appraisal discussions regarding my poor performance, which never happened. Infact my appraisal discussions was always good. Now HR is simply saying NO for which they even don't have any justification. Company has mentioned the annual incentive amount in my increment letter as well but has mentioned this point that it will be based on my performance. I guess, company is not paying this amount from their pocket, infact It is a part of my annual package which company is keeping with them. When I got promoted (on 4th Aug’16), my revised total package was Rs.9,51,437/- in which company kept Rs.1,20,601/- as annual incentives & now they are refusing to pay this amount. Are they doing right..?? Can anybody suggest me what I should do..?? I would appreciate your valuable feedback in this regards. Let me know if you need any more information. Thanks in advance.