The same incident happened with me.. I was updating my phone on 3/7/2020.. While the update was getting installed, the screen started flickering and started behaving abruptly.. I am unable to use my phone ever since.. Going to the service centre didn't give me a resolution because they didn't even look into the matter and suggested a new display at a whopping price of 17k..
My phone was well kept and there was no accident as such so how could a hardware fault rise..
Samsung is into something very fishy...A new tactic to promote the sale of new flagships by raising issues in the latest update for s9 plus..
Dear Samsung Member,
Greetings from Samsung Customer Support!
Please perform the below mentioned steps to resolve the issue:
1. Adjust the brightness
Settings > Display > Adjust the brightness.
For further assistance, register your concern in Samsung Members Application (Open Samsung Members Application > Get help > Send Feedback > Error report/Ask questions).
Thank you for writing to Samsung.
Samsung Customer Support