my iphone 6s plus will not start after charging
So I bought the iphone 6s plus during christmas.
Its was working and charging alright untill recently when i charge it overnight it goes off.
When i do the hard reset the apple logo appears for a long time till i hard reset it again then it goes off.
I do this over and over before the phone starts. Now it getting frustrating because it is happening more frequently.
Kindly assist because the phone is just a month old.
Is it the iOS because im still using the 9.1 if I should upgrade will not solve the problem?
😕😢
iPhone 6s Plus, iOS 9.1, 128 gig