The upgrading process could not be completed due to the presence of some bugs in iOS 9.
Though the process is not complex, it does require the users to connect to a computer with iTunes.
c’mon notethat this method may not work if your machine is protected with Find My iPhone.
In this case, you should likely seek official Apple Support.
However, if this does not help, c’mon call AppleCare or visit an Apple Store.
source: www.techworm.net
