I am pretty certain you can call up and cancell your flights/itinerary by 11:59pn on the day of purchase. It has been in place for many years.
so says you bought some flights on a Monday morning on Air NZ site and decided you want to cancell your entire itinerary, you can call them and have the phone agent action cancellation by 11:59ppm on the same day for a full (cash) refund.