This negative feedback will remove once you remove your negative feedback in my account

You are seller right so basically you know the term about giving personal warranty.
Resetting or erasing all setting in iphone will be automatically not cover in warranty. And you are the one who reset the iphone right? It means it is your own problem not mine and it is not cover by personal warranty because any upgrade or resetting iphone will not be cover in warranty. Try to look around in sm cyberzone or cellphone stall it is not cover in there warranty see for yourself.