Need to remove subdomain permantly

That “error page” is the expected behavior for domains that are not in use. The page you see is a fallback page for domains that are not assigned to any account.

If you owned the domain before, are concerned about people still visiting that domain and want to have some influence on what people see when they visit the domain, the simplest way to fix that is to simply add the domain to one of your hosting accounts. That way, you can choose what to do with it: display a notice that the site is unavailable, maybe promote your new website or just redirect the old domain to your new website.

I also merged both of your topics. Please don’t create multiple topics about the same issue.