Myntra.com — Not delivering my order and refunding without my permission

I had placed an order on 20th September which was meant as a gift for my younger sister The very next day of delivery when I checked the status it said that the item went out of stock during processing. While till the morning on 29th, it was still in stock but was available at a higher price and in the afternoon after I checked my status, it was out of stock. Just because I had ordered at a discounted price, my order was cancelled. I feel cheated and when contacted they said that they can remind me again when the product would be available again and can do nothing about it! Is this the way customers should be treated? I was very disappointed and angry at the same time. Myntra is cheating with the customers and they have to be taught a lesson. I will take this issue across platforms and even to the court if they do not come up with a proper resolution.