SuperSize handling can be funky. I hope you kept a print of the original receipt and/or the emailed confirmation when you purchased the SuperSizer.

I'd suggest you send NW a copy of the itinerary -- clearly noting & numbering each segment. Then add a copy of your WP mileage postings with those segments highlighted and a copy of the SuperSizer receipt and/or confirmation.

I would send these (snail mail with brief, to-the-point cover letter) to: