Q: Black Shadow top left corner iPhone 6S - 64GB GOLD

I own the iPhone 6S - 64GB GOLD bought it in November 2015.I am wandering if anyone is experiencing the following concern that I have below or have any solution to it:

Across the top of the screen on white backgrounds there seems to be a dark shadow cast from the edge.The dark shadowing is the corner near to the "Volume/Mute button" . The corner where it display the network coverage signals from the service provider.

I had called apple store and tried to get an appointment in Mall of the Emirates, Dubai but they are so busy and fully booked because we have only 2 Stores available in the whole Middle East region and as per the Customer care representative the whole region comes to these two stores to get their products checked and fixed. I would like to know if anyone had the same issue and got it fixed or resolved? I am a person who take cares of the phone like a baby, always in covers and screen protector. Never dropped and encountered water damaged. My iPhone is as brand as new with default packing. I used it very less.