NEED HELP! iPhone 6 with black screen!

Earlier today i was using my iPhone 6 perfectly fine. Then when I came home and made a phone call, checked out social media. During the middle of using it the screen just went out. I thought the phone died at first, but when i plugged it in to the charger, i heard the charging sound. I took a really close look at the screen, and i can still see the icons! It is still responsive and i can see the color but, it is completely black! I tried going to settings - general- reset- and rest all setting. I tried a hard reset and even a complete restore. Still nothing! I went to the apple store and they said they can't fix it, and gave me no reason why they couldn't. Any suggestions for DIY?