Hmm, weird that you still can't call this specific 0900-number. You still got the same voice message that the number doesn't exist? Normally this isn't the notification you get when 0900-numbers are blocked.
I also asked one of my colleagues to check if the service numbers are also unblocked in our underlying system. The service numbers are unblocked. In your first message you mentioned that you can't call a specific 0900-number. May I ask what specific number it is? And can you also try to call another 0900- number to doublecheck? For example, is it possible to call 0900-1884? This is the number of the Ziggo Customer Service, but in this case an easy number to test. Please let me know if that's possible and if not, which notification you get.