I am only guessing, but there is TNZ, VNZ and NZC so I think TNZ is probably Telecom, VNZ is probably Vodafone and NZC is probably 2 Degrees.
Product Manager @ PB Tech
Good news for Samsung ATIV S users as the handsets are reportedly receiving a large update today: Microsoft’s Windows Phone 8.1.
While many of us are already running the latest version of Microsoft’s mobile OS, either thanks to regular updates or the Preview program, some users are still stuck on previous version. In fact, more than 36% of users are still running Windows Phone 8.0.
Luckily, ATIV S users will no longer be part of that statistic as many reports are coming in from different parts of Europe, where unbranded Samsung devices are now receiving the WP 8.1 update.