Nykaa.com — Showing wrong offers on website to scam customers

Nykaa had a offer going where in when you buy a lipstick of PAC Cosmetics you get another of your choice free, but that offer wasn't getting applied on the cart and hence on my order. I did mail the company regarding the same and also called it's executives who first denied the existence of the offer. Later on when I sent them screen recording of their app, for a length of 3 days (period the offer was visible on their app), they went down the route to offer ₹200 for a ₹550 loss after dragging the matter for more than a week and lots of denial. Now I seek a fell ₹1100 refund to make up for the mental agony, time loss, and lies spoken by the company at each step.