The best way to avoid any problems with having a UN cylinder filled in a dive shop in New Zealand, is to keep a copy of the import certificate supplied with the cylinder and take it with you each time you have it filled.
If you lose your import certificate you can ask your cylinder supplier to supply a new one or you can ask the Dive shop to access the online database held by Worksafe NZ that shows all the registered UN cylinders. Please be aware this list is not live and it can take 4 – 6 months for this list to be updated, so it is important to take your import certificate to your dive shop until they get to know you.
If the Dive shop is unsure they can contact the compliance certifier that issued the cert.