Problem: shadows on screen

My iphone 6s has a problem on the screen, which was recognized by the assistant manager of the official Apple strore in Florence. I sent the phone to the official apple service in Greece . They told me that the answer of the official store was that “the apple does not recognize the problem of my device”. However the assistant of the official site recognized the problem which is that on the right side of the screen displayed some shadows that are visible in bright colors like white, yellow etc.

Thanks a lot