headphonemanias - Product as shown not delivered

I saw this offer on Facebook, where a smart series watch was available at great discount with Rs ****. it asked for COD and I opted for that. The item was delivered to me by Ekart delivery boy. he told me make payment and then online he will give parcel. After payment when I opened the parcel, I found it is having duplicate fastback watch, with no details available of supplier. I immediately called the delivery boy and asked him, he told he only knows where to delivery and nothing else. he cannot return money and take back product as he declared item delivered and posted the money. I went toe kart warehouse also to find out the details of supplier but they also didn't help. now I don't know what to do.