You can simply over-write and delete the HelpDesk category name. It will no longer appear on the HelpDesk view. The Complaints created earlier with this Category will still show. You can either continue them as-is or change the Category.

Step 1: Login to ADDA -->> Admin -->> HelpDesk Tracker -->> Setup

Step 2: Just overwrite the category you wish to modify or just remove the content to delete the category.

Step 3: Scroll down the page and click on Save Changes.