iphone has never been backed up

If it has never been backed up, now would be a good time to do that.

How to back up your iPhone, iPad, and iPod touch - Apple Support

Once you have done that, try to update the phone. If it doesn't work, please post back with the specifics. Where is the update failing? Are you getting any error messages?

See also:

If your iPhone or iPad won't update - Apple Support