Unresponsive iPhone
I have a new iPhone 6S that developed issues necessitating replacement. I am waiting for my replacement, but meanwhile the phone has become completely unresponsive--will not turn on. I want to back my phone up so I restore to my new phone, but so far have had no luck. I can't even sign into support because my serial number has been disabled. HELP!
iPhone 6s, iOS 9.3.1