Phone wont switch back on after hard reset to fix black screen

My iPhone 6 was working fine up until yesterday which was when I noticed my screen kept freezing and glitching(.multicolored lines flickering on the screen )then I would simply press the power button once to switch it off the back on again and it would work fine again for a moment or two before freezing again so I hard reset it and the problem was fixed . However this morning when I woke up I turned on my phone to check the time and I could see the backlight was on but the screen was black and there were short grey horizontal lines along the bottom of the screen .I switched it off thinking I was still dreaming but it was the same when I checked it again .So I tried to hard reset it and now it wont switch back on