Mobile — Return of mobile as it was faulty mobile but seller refused to take return.

I order a mobile from seller and it was for Cash on delivery and when I received a product and paid them through ecom express. As I opened, it was a faulty mobile, it was not even turning on, the same moment I messaged seller about the faulty mobile within 15 mins of getting the mobile, he refused to take return of the mobile. It was in seller conditions, that you can return the mobile within 15 days. But now he refused to take return and also refused to refund my money.
Kindly take a strict action on him and help me getting my refund.
Sharing his ecom express AWB [protected].
I also have all the proof of his messages stating 15 days money back guarantee.
Attaching all the screenshot of evidence.
The evidence is whatsapp conversation where you will also find his mobile number.