Online Marketplace Store India [Omsi] / Online Medical Store India — Regarding a Product I ordered 2 months before

Address:

Online Market Place, D-41, Fourth Floor, Andnd Vihar, New Delhi-110092

I have ordered 2 Food supplement for My dad in Kerala through OMSI on 26th January 2021. I have paid extra 500 Rs for shipping for fast delivery within 72 hours.. All together I paid 3914 Rs.
For weeks I have not heard from them. When I messaged them on February they replied to me saying that They don't have the exact product and they will be able to give replacement. I said I don't want the replacement and want the exact product. Since then they don't send me any update and recently they are saying that They cant deliver the product and if I want, I can request for Refund. But the catch is, they will deduct 100+5% Tax as the customer is requesting Refund.

I found this as a fraud case as, either I was not informed about the Product and showing disrespect in a way that I have been asking Refund.
It is their responsibility to inform the customer about the product and do the full refund. where they still haven't come back to me about the product. Since last week, I was in a hope that they will still deliver the product. But they still dint reach out to me even after 2 months and dint refund me the full money.