Flipkart private limited - Flipkart has denied to replace my defective product

I have ordered a smartphone called realme * pro from Flipkart. After delivery I found that the phone is defective. The proximity sensor isn't working. So I requested Flipkart to replace the product. A technician has visited the product and found that the product is defective. But Flipkart is denying from last * days to replace my product. I want full refund of my product or replacement . This is really annoying.
My order id - OD******************
Order placed on - **nd January
Order delivered - **th january