Apple India — Apple Iphone 6s

I have submitted my i phone 6 s with a complaint of small white spot on my display. But they couldn't service my phone and replay me with below details

Ticket no. Sck43867 (My service ticket number)

As per apple service guidelines iphone can be replaced under exchange price.
Amount to be paid rs.28139

Still i am using the phone for my regular works and no other complaints, even the warranty period is still there why don't they not service my phone with free of cost.. I don't want to replace my phone i just want to clear the complaint..

I don't like to submit my i phone 6s to an un authorised service centre

Even new i phone 6 s price is only around 26000 and why the replacement price they quoted 28139