Myntra.com — Exchange product wrongly picked along with return

I bought 3-tshirt & 1 tracks from Myntra and all had size issues, so I requested for 2 return and 2 exchange. Next day, a guy came to pick up & all 4 products were handed over to him.
But the message confirmation says only 2 return item received. When I called the delivery person & asked, he said he had sent alI 4 products to Myntra.
Now I am unable to receive my exchanged product because they are asking for the old product which is already given to Myntra. I have raised so many complaints with Myntra, they are simply denying that it is not received.
It is Myntra's fault that their delivery person is not provided with right information and we users are struggling because of this. We are loosing time and money.