My iPhone 6s has a black screen and turns on sometimes but when the screen timeouts i can't get it back on
Can anyone here help me on my "dead screen/black screen" iPhone issue?
I tried hard resetting (holding the home button and lock button simultaneously), connecting to iTunes (unfortunately I have a passcode which I cannot input since my screen's dead so yeah can't access my phone on iTunes), I tried home+lock+home again (a developer combo) and have charged my phone for a hour now but none of these solutions worked.
I know my phone is still working since it still vibrates when I change the notification toggle (?) on the upper left side of the phone. I also tried calling and have successfully answered a call but the screen still won't turn on.
UPDATE: the screen turns on sometimes but after it the screen times out or locks, I can't get it to turn back on again. Please help. The nearest apple service center is a 14 hour trip from our place so please please help.
iPhone 6s, iOS 9.2.1