1. Log into your Merchant Center and navigate to the "Contacts" tab
2. Click the gray "Manage Lists" drop-down menu in the top right-hand corner and select the list you would like to delete
3. Click the gray "Edit List Settings" drop-down menu in the top right-hand corner and select "Delete"
4. Click the check box to indicate that you understand deleting this list will delete any auto-sending settings assigned to the contacts within the list
5. Click "Delete List"
This will only delete the list itself and will not remove contacts located on that list from within your Merchant Center.