Dave Noble - NZ do not charge any extra to go from economy to business regardless of what fare you booked. They see it as not a fare change but a product change from Y to J.
Nux - I am not offering them anything other than what there system tells me is the difference is price between the products. Sure they also saying they want cahnmge fee and I am saying no. Thats is why I see them loosing, may not be strictly a good arguement, but I am asking to change product not not fare.
Never mind lesson learned, must double check before booking or just go staright to what I want and stick with it, as after all like some one pointed out, logic and the airline industry does not seem to go hand in hand which is why last minute fares are so high, they would rather fly with empty seats than take less than full fare.
I'll stick to my day job 'cos i ain't ever gonna be able to unnnerstand money things.