Amazon India - Product Returned and refund denied

Earlier amazon delivered me a different product which I haven't order and only of the executive had only requested my return pickup for the same issue and after returning the product amazon declined my query by saying you have given us the different product and now they are not refunding my money back and threatening me daily that they won't give a refund for the same. I request you to please help me in this regards and try to get my refund back as soon as possible as I am having an issue and the refund amount is too big so please it's my humble request to help me, please