Like every other service. They warn, freeze access and give you a period of time to pay.

What happens to your files when you refuse to pay the bill?

I wouldn't. I've explained what I want.

There isn’t an option to not resolve “you’ve reached your billing limit and now storage charges are exceeding it.” You can resolve it by unceremoniously dumping the user data. You can resolve it by… continuing to charge the user, and holding their files hostage until they pay the back storage charges, and then the egress fees (so, it isn’t really a limit at all). Or you can resolve it by just giving the user free storage by some other name.

Just saying that there should be a limit is not an explanation.

I said you could put the limit at 1 trillion dollars if that's your concern. there's no limit for you!

(for my hobby projects, I'm happy for the limit to be $5 and delete everything when the limit is reached. that's what my backups are for.)