hmmmmm... it's a tricky one

ultimately it was a reward flight... even though you paid for the First upgrade, what exactly would they credit? You wouldn't be entitled to the regular First miles/points rumuneration... and they can't base it on the fare paid as the base fare was a CW reward flight which you aren't entitled to earn anything against. what have you asked them to credit over? because, painful as it may be, it really does sound like an invalid claim...