OnePlus India — Manufacturing defects

My phone has a manufacturing defects but service center employees says we can do anything you have to pay for it.
It's had not even a month my screen is completely gone black because of defects on screen with no external damages.
I have not faith in service center employees as they have talk rudely with me and have no sense how to talk to customer absolute pathetic service.
I have faith in OnePlus higher authority who can resolve my queries with no fault of mine.