Sign in and visit your "My Account" page. In the right column, under "My Listings," you'll find a list of your directory listings.
Each one has a "Manage" link button that will open the "Listing Summary" page for that listing, there you can click on the "Order Information" link button that will open that page showing the "Order Details" for this listing, at the bottom of the form, you'll see the red "Cancel Order" button used to request removal of the listing.
Keep in mind that you can always edit your listing as well using the "Edit" link. This option should be used in place of deleting a listing and starting from scratch.