Amazon India — product returned but they are saying empty box received

Address:	Jodhpur, Rajasthan, 342001
Website:	www.amazon.in

I have purchased a lenovo k8 note mobile from amazon site on 16/03/2018 (Invoice number: del[protected] for rs.11999/-. While using the mobile i found that it was discharging very fast, then i talked to amazon technical team and they tested the mobile online and found that there was a problem in the mobile. They told to return the mobile for replacement. Since my job was transferred from chittaurgarh to jodhpur, i told them if possible please collect from my home town at udaipur but they told to send via courier or preferably by indian post.
I sent the mobile via indian post on 28/03/2018 from jodhpur and same was delivered on 02/04/2018 (As per indian post tracking details). I was contacting daily to amazon about the product receipt and refund. After so many phone calls amazon informed me on 07/04/2018 that the box received at their end is empty. I complained at indian post, they have replied that “the item was booked with proper packing, no physical harm or manipulation done to article. Item was sent in safe and sound condition”. It seems the problem of amazon.