Robert The only case you can go over draft, but then your account gets spending blocked, is when you execute a credit card payment on an off line terminal, like on a plane.
Max payment in this case is 250 Euro and if you do not have that amount available, when the terminal gets on line and execute the charge your bunq account goes negative.
In this case bunq blocks the account (and you get a notification) and only when you deposit an amount to get positive balance again then the account gets un frozen.
Bunq does not offer credit.
Regards
GG