That's one thing. The second thing, I'm happy for you that you have more information about their pricing system than their pricing page and terms of service page state.
Also: https://support.bunny.net/hc/en-us/articles/360000235911-How...
But yes, other services will run until your account is dry, then it gets suspended. You can't set a spend limit on your scripts without it taking down the whole account. You can't do cost optimization, but at least you are protected from going bankrupt.
I once had some pretty serious DoS attack, but fortunately, I didn't had to pay more than what was pre-paid.