India Post — product sent but receiver received an empty box

Address:

Kolkata, West Bengal, 700084

We have sent an electronic item jbl bluetooth speaker from post office sp garia so 700084 with no ew[protected]in. Counter no.1 op-code: 06

To govind sundesha mumbai maharasthra pin: 400002
Sender dipangshu saha kolkata 700084
Weight 925 gm on 26.05.2018 time 12:09pm

Amount 142.00 was taken from me. The receiver received a packet written 925 gms but there was no product inside the box.
The man who came to deliver the product just gave the product and ran away no sign and nothing as per the receiver. As it is his shop that time he was not present there. The man gave it to someone else and just flew away.

Now what should i do. I relied on indian post thats why i sent that product via them. Otherwise why would i? Please give me a solution.