It's Vodafone that's caused the original issue here. Number porting in the UK is controlled by the donating network. Problems like this occur when the donating company doesn't release the number fully. Vodafone have a unique way of porting and so cause more errors then the other networks.
You'll need to call o2 customer services who will need to escalate the issue, this is done by filling in an electroninc form. It's proper name is an 'MNP Escalation' so if the advisor you speak with is needing some guidence use this term and hopefully they'll manage to put 2 and 2 together.