I have been a QUITE satisfied Apple consumer for more than a decade until recently. My iphone 6S plus had a frozen screen and completely turned into "brick" during the attempts of IOS 10.3.3 restoring. Sent the phone to apple repair service and was told that the product is ineligible for service due to "unauthorized modifications". As the phone looks like brand-new and has been carefully protected in a case after an early incident I reached out several senior advisors and requested for some clarification. I have been told that 'unauthorized modification' means the "unauthorized replacement of screen or battery'" But arrogant Apple advisor don't bother to provide any details. I disagree with the statement as the phone has been with me all the time except an incident last year detailed as followed. I purchased an expensive leather case on apple.com. However, I accidently dropped the phone on the tile and cracked the screen. To my surprise, this beautiful and expensive case didn't provide any protection at all as the edge of this case is even slightly lower than the phone screen. As a result, I mailed the phone to apple repair. I just realized that the serial # of this phone was different from the original phone. Apple advisor said it's a common practice to swap the original phone with a refurbished phone to accelerate the repair service. As no detail/evidence was provided by Apple, I can't figure out what and when "unauthorized modifications" were made to this "brand-new looking" phone. Apparently something fishy occurred during the only mail-in apple service a year ago. If the phone didn't have this 'brick' issue, we will never uncover this dirty trick. Any idea about where to complain about Apple service?