Quikr — Mislead By The Seller Want Refund PROMISED REFUND AND NOT YET RECEIEVED

Hello Sir,
We had booked a product on the below website link

https://www.quikr.com/electronics-appliances/call-whtsapp-sony-ps4-pro-and-ps-5-...⇄

initially they asked to pay Rs.6000, we made the payment and when asked for confirmation email, the seller demanded for more money Rs. 2750 saying delivery charges and later said he will give that back as cash back, and after collecting this amount, I have not yet recieved the product and when called he asks for more Rs. 3000 saying GST, please blacl list such sellers from your site, as its pulling your reputation down.
I am approching uou 1st to get my refund and will appreciate for the same else i have no other options than reporting them.