Step::1 Login to your WHMCS.
Step::2 Hover over the Setup section to Products/Services option and click on Products/services.
Step::3 Now choose any product and click on the Edit icon.
Step::4 Scroll down to the bottom of the page and tick on Hidden option.
Step::5 Click on save changes.
That's It !Check out the video tutorial on the same.You may checkout the blog as well.