Not getting my experience letter and f&f settlement after 7-8 months

I left my last company in June/30/2017 after 2.5 yrs of service and duly giving a 1 months notice period. I offered to abide by the same and during my notice period did my complete handover. My immediate reporting boss approved of my resignation and had sought from the internal HR team to relieve me as per my request i.e. within 1 month. After all the handover, I left the co on 30june 2017 and regularly followed up with the HR to provide me my releiving letter, work exp letter, FnF (KRA AREAR, BALANCE LEAV BOUNUS), and dues. The HR has not responded back even after 7-8 months. visit the factory many time asks HR and they did't give and sometime HR told me to contact with HO Mumbai. Even mail 25-30 mails but no result. The HR has not responded and I am still waiting for my dues Please suggest as to what is to be done.