No idea what APN is (Access Point Name?) or why you think that you are getting "ghost tickets". But if for some reason you are getting tickets that are not associated with a department or team then you will continue to get them until you find and correct the issue that is creating it.
It's easier and faster to just wipe the whole database and start over.
You would want to delete the contents of the following tables:
*_attachment
*_draft
*_file
*_file_chunk
*_form_entry_values
*_note
*_organization__cdata
*_session
*_syslog
*_task
*_task__cdata
*_thread
*_thread_collaborator
*_thread_entry
*_thread_entry_email
*_thread_event
*_thread_referral
*_ticket
*_ticket__cdata
additionally if you want to remove all the users you would also to
*_user
*_user__cdata
*_user_account
*_user_email