Myntra.com — Cancelled my orders on their own

I had placed an order(Order ID # 1155923 [protected]) on 30th October 2020, there was an offer running buy 1 at 599 and 2 at 999. I bought 8 items, it was a prepaid order. But one by one my orders are getting cancelled, with no proper response ( internal issue they are claiming) while the products are still in stock, and even one of the product was even shipped. PFA screenshots of the same. I feel cheated, just because I bought them at discounted price, how can they cancel my order. Till now 3 are already cancelled, tomorrow there are chances they'll cancel each and every item I ordered under this offer.
The offer was provided from their end, while the product is still in stock, how can they cancel it.
I want to take legal action against such fraud.