Unfortunately the app doesn't work for business users (the App Store description has always said so); I've been told that business users use another area of the O2 website for account management and so I'm looking into supporting business users, but I can't promise that it'll be available any time soon.
Apologies that you didn't see it; feel free to contact iTunes customer relations via the Apple website if you'd like a refund (they deal with all of the App Store's finances, including formally-requested refunds)