iPhone won't turn on at all and doesn't even show the battery symbol

I dropped my phone yesterday and the screen just went black, I was on a call at the time but the call carried on I could still hear my friend, it was illuminated so the screen came on it was just pure black and I couldn't go to the home screen or turn it off or anything, in the end I just hard reset it using the home and power button but then I wouldn't come on at all wouldn't show that it was charging or low battery anything. Really need some help with this as I've tried changing the battery and checked to see the display was connected properly but it was all perfectly fine, I have no idea what the problem is.