Shoppers Stop - Not exchanging the product or refunding my amount even after 25 days

I received the ordered item on ** June ****. Later I returned * kurtas out of * because of size on **th June ****. Courier agency picked the item on **th June. But till date I.e. * july ****. , I did not got my exchanged item or any type of refund.
Now after emailing *-* times to customercare@shopperstop.com and calling their customer support executive *-* times , today they are telling me after almost ** days that your order has failed the quality check. Therefore we are returning back it to you. When I asked which quality check, they did give any response. This is ridiculous. I have not used that kurtas nor even wear it. I returned it only by seeing the size. I don't know which quality they are talking about. How can such a big company make a false claim to hide their fault. What can I do to get my refund.