Paytm.com - Door lock delivered in place of iPhone

On * May ****, I ordered a ** GB iPhone * from e-retailer paytm.com. I paid Rs **,*** upfront through my bank debit card. On ** May **** I received my order by courier. On opening the box, I found there was no phone inside, but parts of a door-lock assembly with screws. I took pictures of the contents and emailed them to paytm. I put in a formal request for them to take back the package and refund my money. Paytm customer care apologised for the incident and assured me a speedy resolution. They had me sign a disclaimer which I emailed them on ** May. After numerous calls and emails, paytm finally emailed me on ** May saying a full investigation, including pre-despatch x-rays, found that the correct product was delivered to me, hence they would not refund my money. When I asked if the package had been x-rayed at the Guwahati courier before delivery, they refused to share details. I have written multiple letters to the paytm.com grievance cell, all to no avail.