Fraud by Blinkit in Bangalore

Ordered 5L + 1L oil from blinkit. Advertised as 5L + 1L on the app for Rs. 1072. Delivery agent delivers only 5L. We raise a complaint with Blinkit and request either give us the full order or take back the 5L. They now say that they will give a Rs. 100 coupon against an item that was 1072/6=Rs. 178 because it's the maximum that their policy allows. They further claim that 1L oil was free and hence no value can be ascribed to it. What is the recourse available against such frauds?