1. Log into your cPanel account.
2. In the Domains section, click on Subdomains Icon.
3. Under the Modify a Subdomain list you can see a list of subdomains.
4. Click the Remove option under the Actions tab.
5. You will receive a warning that you are removing a subdomain.example.com. You will need to click on the Delete Subdomain button to remove your subdomain permanently.