Apple India — iphone 7 colour black matt colour is disappearing

My iphone 7 black matt colour is disappeared and it is in warranty and apple is not changing my phone.
I have coordinated with apple support center and they said we don't give warranty on colour.
I didn;t spent 60, 000 money to hear this statement.
If i have bought their phone, they should be able to satisfy their customers needs as well as if any customer face the issue.
I didn't use any cover but still my colour is disappearing day by day.