Why is the fare online higher than the advertised price?
Air New Zealand often advertised special fares which often have restrictions around date of booking, length of stay, dates of travel etc and are usually advertised at the starting fare level.
These fares also subject to availability and they sell out quickly! It is possible that the fare that you were quoted online is higher than the advertised fare because the cheaper fares have sold out on your chosen flights. Try changing your travel dates to find the cheaper fares.
How do I get the fare I want?
To help get the best fares, avoid peak travel times - like school holidays - if you can. Some fares have lower prices for travelling on weekend instead of weekdays.
The more flexible your travel dates and times, the more chances you have of getting a lower fare.