Cedric-Grey-Unicorn This is just an assumption based on how bunq works, but I think you can have a business account and a personal free account. A free business account doesn't exist so you need that one for the cards, and then I think you can set up a free personal account and link your business card to that one free personal IBAN.
But to be sure, you could try it, or wait for a more experienced person to react. Or ask private support. :)