1. log in to your DirectAdmin Account.
2. In the Account Manager section, click on the Subdomain Management Icon or type Subdomain in the navigation filter box and then the option will appear. Click on it.
3. Under the Subdomain Name, Select the subdomain name you wish to remove.
4. Click on the Delete button, If you also want to remove directory contents then checkmark Remove Directory Content and then click on the Delete button.
Your subdomain will be successfully removed.