Unfortunately nobody anywhere has a resolution for this problem. I too am in the same situation. It seems that the standard response from O2 customer services is "wait 24 hours" which is more annoying than the actual problem itself.
Regrettably the level of service from O2 has dropped rapidly and since they merged with Virgin it has got even worse, Anyone upgrading or getting Virgin services are forced to take an O2 sim only. This helps inflate their customer base to an extent where they cannot provide adequate support when issues arise. This issue with the Apple Watch and the data plan seems to have gone on for a long time yet O2 are still allowing customers to sign up for it.
It's a disgrace and totally unacceptable.
