I am also having this problem. I bought a sim only plan from Carphone warehouse and have a PAC code to transfer my number to Virgin. However I can’t create an account as I am being asked for a security answer that I haven’t set up.
I've got the same problem: I'm trying to register but my security question is set to blank. I tried calling 789 but it just re-directs me to the online help which is of no use. Could anyone, please, help me out?
Please can you tell me how on earth I register my Virgin Mobile account without knowing the question, and cannot give the answer!!
Also, I've received my mobile as part of the package I signed up for but that 12 month contract does not start until 5th June and will end 4th June 2021. When will the Mobile contract end? (I've not activated the SIM yet as want to make sure it ends same time as the bundle contract).