Amazon India — product not delivered but showing delivered in portal

Address:	Kolkata, West Bengal, 700050
Website:	ww.amazon.in

I have ordered a redmi 4 phone on 23rd sep 2017 and payment done online. On 25th sept we noticed that the status has been updated as delivered even though we haven't received the product. We called amazon customer care and they told to wait till 27th sept as they would launch an investigation. We called again on that day and then they said to call on 3rd oct for the investigation outcome. We called them on 3rd and 4th oct without any outcome and no satisfactory reply from them. Being an amazon prime customer this is completely unacceptable and highly disappointing