You may use the Force Exile from the book Angels of Wrath . That works fast. You should buy the book but it will do wonders oın other issues you may encounter sooner or later too.
Also, Prince Sitri will help too. Though He is most famous for immense sexual passion; He is a Prince of Darkness and holds many powers. If you are familiar with Sigil magick; you 'll do it easily. He may take time but once he forces them, they will leave at once.