How to Remove an Add-on Domain?
1. Log into your cPanel account.
2. In the "Domains" section, click on the "Add-on Domains" icon.
3. Locate the subdomain under "Modify a Subdomain" and then click on the "Remove" link.
4. Click on the "Remove" button once more.
You should see a success message notifying you that your Add-on domain has been completely removed.