Apple India — defective apple ipad received from amazon. authorised apple service provider denied service under warranty

Address: Nyasa, City One Mall, Pimpri Chinchwad, Pune, Maharashtra

I purchased an ipad from amazon on 08-september 2018. I'm using the ipad with a protective cover purchased from amazon itself from day 1. The ipad got a very minute dent on back panel 4 months back. Since yesterday the screen is showing some linings indicating that the internal display is damaged. I had been to nyasa which is an authorised service centre of apple and they denied servicing under warranty. My more than 6 months of warranty is still there. Just because they don't want to service it for free, they are demanding 21, 500 inr to replace the ipad.
And they are saying that ipad has gone physical damage and the minute dent has caused internal screen damage. This is very wrong. Just because they don't want to service it under warranty, they are blaming this issue on the dent which had occurred 4 months ago? After that i have been using this ipad and there was not even a single problem. How can internal screen damage occur after 4 months? I have received defective product from apple. And they are denying service. The apple authorised service centre is fraud. When you go with a problem, they start finding 100 new problems to charge you.