You cannot permanently delete work orders from out in the field. This must be done from within the office. The only work orders that can be deleted from the field are work orders that have not been sent back to the office via synchronization. For instance, if a work order was created in the field and has not been sent back to the office yet, then field users can permanently delete it.
Hint: Work orders that have not been sent back to the office via synchronization have an FWO prefix in the work order number.
Additionally, work orders that have already been checked out to the field should not be deleted in the office. If a WO checked out to the field is deleted in the office, the synch process will add that WO back in.