Welcome to the community and thank you for your post. I'm sorry to hear that you've been having log in issues with your Oomph SIM and registering online.
Do you have any other SIM's or handsets with our mobile teams? When you try to register does it also ask for a security 'memorable word' or is this what you mean by asking for mothers maiden name? I'm sorry for the issues trying to contact us also, have you since spoken to the team?