Greciilooks women kurta set - An item missing while return pickup

I ordered * kurta set from Amazon in which I put * suits in return. When delivery agent came for pickup I was in college then. He called me and said Ma'am only * kurtas are there and third one is not there, please cancel the return and do it for tomorrow. When I came back to my room I searched for the product which was missing. I asked my Hostel security guard, he said mam I don't know anything he came and he took whatever you kept here in the morning. I complained to customer care of Amazon for the fourth or fifth time. Everytime they said your issue will be resolved. But today again I called them, this time they said that mam your investigation is denied . We can't help you regarding this. This is very disgusting for a customer.