The update stopped halfway through, came up with the connect to itunes symbol and told me I have to restore the iphone. 24 hours later and the phone has not restored and the software is still not updated. Disgraceful.
Were you updating the iPhone over-the-air?
Did you see an error message when you tried to update the iPhone?
This Apple doc is a good place to start -> iOS: Resolving update and restore alert messages
Retrieving data ...