I've had this error before. My fix was to restore the phone to its original state by doing Settings >> General >> Reset >> Reset all content and settings. Make sure you do a full icloud back up first. Then perform the reset. Once you reset, do the software update. It should work for you...
I've had this error before. My fix was to restore the phone to its original state by doing Settings >> General >> Reset >> Reset all content and settings. Make sure you do a full icloud back up first. Then perform the reset. Once you reset, do the software update. It should work for you...