Backlight bleeding will look like a patch of light coming from the edge or bezel of the screen.
To see if this is what you are experiencing, please set the phone to a plain black screen.
You can do this just by searching for a flat black photo and zooming in. This will not be visible if the screen is locked or the phone is turned off.
The build of some phones may appear to be a backlight bleed along the top and bottom edges of some phones, however, if this is not patchy or uneven, it may simply the make of the phone rather than a fault.
Unfortunately, in the instance that your phone is displaying backlight bleeding, the only fix is to replace the screen.
Please contact our support team with photos of the issue, and we can let you know if we can cover your claim under warranty.
If this is simply due to the build of the unit, or if the phone has sustained non-warrantable damage, a screen replacement will not be covered under warranty.
If your phone is displaying backlight bleeding, please feel free to contact our Support Team via our Help Desk here, including clear photos of the issues as well as a copy of your original invoice, which can be obtained as detailed here.