no it isnt crap since the system is there to protect from fraud.
that your credit card have been blocked just says that you have tried doing something that could be seen as fraud.
but as you have been told by Troviak aswell the only way to resolve this is to open a ticket and talk to Blizzard.
I stand by my reply → check Parental Controls.
that dosent automaticly turn on and since he already have tried buying stuff already and his Credit Card got blocked after that then it isnt parental control 
Hey Sinistru,
I’m afraid that we will not be able to discuss your account information or history on a public forum, however please do read the responses that you have received to your tickets, which should explain what happened, and what you can do to resolve this situation.
If the answers are unclear, you can always respond to the last one to ask for more information. 