Amazon India — accessories missing in my received box and company denied to support

Address:

World Trade Center - Brigade Gateway, 8th floor, 26/1, Dr. Rajkumar Road, Malleshwaram(W), Bangalore-560055, Karnataka, India, 560079

I purchased a oppo mobile phone on dated november 8, 2019
But inside the box one accessory (Headset) was missing, then i approach to amazon on their customer service no ([protected] - call back) to register the complaint against this issue.
They registered the case and close by internally, even they didn't inform me about this closer.

Today (15/11/2019) i did call to them to know the status of my complain, then they replied "this is already closed as per investigation team product was delivered to you".