Vodafone NZ currently offer a dedicated iPhone and Android My Vodafone app for account management and reply on a mobile website for Windows Phone. See http://www.vodafone.co.nz/using-myvodafone/mobile/
Any chance of a dedicated Windows Phone app from Vodafone NZ?
I would love one! There is of course a cost involved, however I am about to start discussions with Vodafone on the subject of building it. I am confident we can make it happen. TIming is a bit too fluid to be able to provide a date yet though.