i have had my iPhone 6S Plus for over a year now but just yesterday the 20% battery warning appeared and then my iPhone 6S Plus automatically shuts down. When I try and switch it back on I get the empty battery icon with black background. Anyway, when I connect my iPhone to the charger it displays 14% on the battery. Something is not right here. My iPhone shouldn't shut down with still 20% battery left. I went onto the Apple site and typed in my serial number to see if my iPhone was one of the affected units with the defective battery but according to Apple my iPhone isn't one of the defective units so I cannot get a free battery replacement. This totally sucks as I have only had my iPhone 6S Plus since November 2015. I am certainly not willing to splash out nearly £1000 on another damn iPhone. Please advise.