The problem apparently locked iPhone screen with black screen.
O 6 issue recently seen on iPhone most the new version of iOS 9.
Totally dark screenWithout any trace of light or give any sign that would respond to a command buttons. iPhone It seemed totally dark and could not open by pressing the Power / Sleep.
However, the surprise was that sThey could receive callsIphone call, but could not respond because the screen does not appear nothing more than black.
Causes and iPhone display resolution black / dark
If I described above, with the iPhone, whose screen is not opened at all, we suspect that was a problem because storage space full.
Before you put the iPhone in a box and have it ready for service, you should try a restart "cold". A forced restart of the iPhone. Hard reset.
How to restart an iPhone 6 / 6S - Hard Reset iPhone
Even if nothing appears on the display, We loaded iPhone (To make sure the battery is), we let it load time 5 minutesthen Home and Sleep buttons simultaneously press (Button lock / unlock side - right). Keep the two buttons pressed for 15-20 seconds.
Normally, after this time should appear white or black screen with the Apple logo (apple) and phone to start normally.
After the restart applications installed documenentele, pictures and other data stored on the iPhone, will not be affected.
If this method does not help, try putting iPhoneDFU mode/Recovery Mode. Need a Windows PC / Mac OS X with iTunes installed, data cable and some attention. this tutorial will not help.