my iphone 7 plus jet black back side got full of white dots

Hi am vikki, am using iphone 7 plus jet black. My phone backs side got full of white dots and i attached the image of my phone that looks so weird. i can't able to read what they printed on the back side.... and i went to service provider they said we can't able take this as problem we have only authorized for hardware and software issues and they said if you need to fix this you have to ask and raise a complaint in apple they will help you. most of the jet black got this dots...Seriously this is so disappointed for all the user. so kindly give the solution of these or kindly replace my phone