Send it to BMW? They'll laugh. This is a garden variety rip off- happens every day in retail. BMWNA might care if you had PROOF. You have nothing. BMW will do nothing more than say "this is an issue you should take up with you BMW retailer".

Have a heart to heart with the GM- have the plugs to show him. No getting crazy, no yelling- just 'your service team let me down and YOU need to know'