I've tried restarting it many times, have charged with multiple different outlets and cords and plugged it into my computer. Still doesn't work...
iPhone 6, iOS 9.2.1
Look here for some help. Look at the last suggestion about putting the phone into recovery mode.
If your iPhone, iPad, or iPod touch won't turn on - Apple Support
None of that works. When connected to iTunes it does't work either.
IF recovery mode will not work, which is basically your last hope (assuming that you charged the device for at least an hour or so) then you need to contact Apple Support.
Contact Apple Support if you can’t update or restore your device with recovery mode, or you can't use recovery mode because of broken or stuck buttons.
My iPhone 6 is black and won't turn on
