It looks like o2 have recently carried out a migration of their billing systems. During this migration they have not successfully moved over customer accounts details properly.
What this means is, the current email address + any other details you're using has not been migrated over to there new system correctly at all and you will need to call o2 to resolve this.
They will ask you to use a new email address moving forward as they apparently couldn't migrate over your old email address from the old system. This is a complete IT failure on their part for whoever is managing that migration project.
Following getting a new email address sorted, the next step is to go through account activation and verification. They will send you an activation email to your new email address and proceeding that, they will get you to verify KBA. This process is tedious and buggy. I'm currently on the phone to them as they cannot verify my direct debit details which I have been using. Leading to longer wait times and the person on the phone seeking technical help.
This is absolutely appalling from o2 business / IT development teams how can they roll out this new system live to customers in this state?!
