Yepme is not processing refund after return of product from last four months

I had purchased a product from yepme and had issue with product.
I raised request to return product, Yepme arranged return pickup on request.
I have returned the product but they are not returning my money back , First they used to tell they did not get product.When I said it is their responsibility to track product as pickup was arranged by them. Now every time i cal customer care they tell they require 4 working days to resolve since 4 months. I have made more than 15 calls since. Can you resolve this issue.