3:20 PM -- Bad news for iPhone users in the U.K. today: Telefónica UK Ltd. , the exclusive iPhone carrier, had a major data network outage that affected monthly contract customers for what appears to be most of the afternoon, and it's not clear whether the problem has been fixed.

The network was unable to carry packet data, so users were unable to access the Internet, and services like MMS were not possible. The operator has not yet provided an explanation for what caused the data network to crash.

This really doesn't look good for O2, which may be about to lose its iPhone exclusivity to T-Mobile (UK) and Orange UK , according to this Mobile Today report.

UPDATE -- An O2 spokesperson sent this statement to Unstrung early this afternoon:

— Michelle Donegan, European Editor, Unstrung