they said that was a "provisioning error" and it has now been fixed.
Where did you read that? Asking cos I'm probably going to switch from T-Mobile to O2, I really don't want to be JB'ing my iPhone.
Apart from being an erroneous out of date duplicate thread posting, you're also missing on the Bill Ray post from before, which is imho more interesting...
http://www.theregister.co.uk/2008/04/09/o2_accidental_call/