Hope you can share more about it because it might help out our friends here especially those with S20 series who facing the same problem.
1) Which service center you go
2) Is your S20 still under warranty
3) Or is there any procedure needed, etc..
I guess those who really facing the same issue might try out by asking Samsung Service Center again about the problem.
2. The phone must have 0 visible damage on screen or back panel.( If have scratches, dent, thats no problem.)
3. Its not required under warranty.
4. There is simple procedure.
Just bring your phone to service center.
Show them display line issue.
They will take your phone. Then they will do water test. (To make sure you didn't do any repair on that phone )
If pass test they will tell you contact in 7days. Thats all.
Important note for free display change.
If your phone have been any kind of repair, so don't go , and don't waste time.