ASAP IT. Each and every time. With time, place, and if possible a recording of the voice of the perp.
Eventually the FAA will decide it’s less trouble just to have the FCC track a few perps down and permanently end their careers ‘pour encourager les autres’ (as the French say) than it is to keep dealing with the paperwork.
By the time word gets around about the second or third flight crew losing their careers, things on guard will quiet down considerably.