In my ISPConfig3 install if a sites get suspended due to traffic limit exceed, if you try to access the domain via browser the next (alphabetically) active site on the server will be shown.
Thats the normal behaviour of the apache webserver. The daefault vhost exists as part of the base setup and it catches * hotsts. If you want to have a default vhost for sites were you used the it, then create a nwe website and use this as domain name:
the domain name does not has to exist, it just have to be the first in alphabet.