Support Assist won't delete cosed support tickets

I have two past support events that have long been closed, involving separate support tickets both of which were assigned the same ticket number as each other. The same ticket number was assigned to a third event which just occurred, and which was closed out successfully. Both of these are still shown as in process. I have called Dell about them and was told they show nothing open and in process on their end. How can I close out and get rid of thes, and why does the same ticket number keep getting assigned?