My phone is unresponsive, and power button is broken

So basically, my iphone screen went black but was still completely functioning, i was receiving notifications, but i couldn't see them, and obviously i'm unable to reset my phone as the lock button doesn't work. I followed my friends advice and connected it to my itunes to restore it manually. But, before i could restore it, itunes said that i had to update my iphone to the latest version. So i downloaded the update and began to update my phone. And it showed up with a message saying that i have to allow my computer access to my iphone by using the actual iphone itself. Now obviously i can't do that due to the black screen!! Please help me!!!