Amazon - Delivery of Wrong product

Sir,
I placed an order #***************** on **
**.**** for Karigari by Unlimited Women's A line kurta worth Rs ***/- on amazon. However, the seller sent a different design kurta of same brand and same color, so, I requested for a replacement and asked Amazon customer care executive to ensure that this time I get tbe design I ordered. But to my surprise the replacement delivered was again the same i.e. of Karigari brand in same color but of an entirely different design. Due to this I had to return the item and request for refund. The item was picked up by Amazon agent on **th October ****. I have waited for refund for ** days now but Amazon still has not returned my money and to my surprise now they are saying that somehow I exchanged the item and returned a new kurta (tags intact) of same brand and color but different design, so they will neither return my money or the item to me.
They flatly denied refund.
First they sent different design kurta and now blaming me for the mixup.
And if somehow I manufactured the kurta howcome the tags are intact and brand and MRP of the product are same? The item sent to me is also available on amazon at the same price. Clearly the mix up happened at their end but blaming me for the same just to extort money from me. This has become a trend with amazon to extort money from innocent customers.
Please help me to get my money back from these fraudsters.