OnePlus India — Product One Plus Nord CE in warranty but had to pay 6875 due to misconduct from Oneplus service center representative

My screen got violet and blue in color automatically. There was not any mishandling from my end but when I approached one plus service center Anupam saket New Delhi representative there asked me there is bend on mobile but no such anything and also what is the relation between bend on mobile and screen display going. It is such a pathetic service from them. This is my hard earned money and they are taking it unnecessary and in unethical way. I had to pay 6875 from my end. If needed I can furnish all the details.
Hope to see any resolution on same.
Address of Service center is below:
OnePlus Exclusive service centre,
PVR Anupam, 11 Community Center,
Ashok Vihar, Saket, New Delhi,
Delhi 110017