OnePlus India — One plus 8T display line issue

Address:

Kerala, Thrissur , Erisseripalam , kodungallur , 680664

I am From kerala, I purchased one plus 8T before one and half years, Now a pink line showing in my mobile display without any reason. There is no damages, scratches in mobile by mishandling it. Then I searched in u tube and communicate with my friends, i there is same problem faced by lots of peoples, this is very important issue from your side.

Kindly help me to solve this problem.
And don't allow to make these kind of mistakes in future.