I'm interested in hearing about other people's experiences with getting imported handsets or handsets not supplied by the network operator up and running on VoLTE here in New Zealand, particularly on the Spark network.

This thread caught my eye.

https://www.geekzone.co.nz/forums.asp?forumid=39&topicid=281579

Were there any issues getting them connected?

Did you need to get the network operator to do anything the allow access? How hard was that to achieve?

What are the differences in operating bands between different parts of the world? In other words are some regions better than others to source an imported handset that will work in New Zealand?

The reason for my question is I am keen on updating to the Sony Xperia 10iii in order to run a VoLTE capable device on Sailfish OS. The 10iii is the only VoLTE phone supported by Sailfish.