Amaron — battery warranty card lost, claim not accepting

Address:

Amaron battery, Thiruvananthapuram, Kerala, 695026

My car battery manufactured 08/16, battery not working. They are not accepting claim because i lost the warranty card.in the battery itself written it's under 48months warranty. So from manufacturing date itself, it's not completed 36 months. How can they denay from giving warranty. New battery costs more than rs 10, 000/=. Looking for advise to get the problem solved.