leehinde I'd expect it to act as though it weren't there.
If the domain uses external name servers like your registrar or another NS provider, then you can do that by un-publishing the related DNS records there.
If it uses Opalstack's name servers, then at this time it's not possible to make the domain act as though it doesn't exist.
As an alternative we can disable the site (not the domain) for you from our end, so that it displays our "no site here" page. If you'd like us to do that then please email the support team.