Dunedin will be the first to lose the service as part of nationwide shutdown over the coming months.
The rest of Otago and Southland will lose 3G coverage on February 3 (see table below for full shutdown dates).
Spark and 2degrees are also pulling the plug on 3G.
The shutdown is to allow the telcos to concentrate on their 4G and 5G networks as switching off 3G frees up radio spectrum, helping boost the newer generation services, One NZ chief technology officer Kieran Byrne said.
Spark will start the process on March 31 while 2degrees began its shutdown on December 14 and is due to complete the work on December 27.
But it isn't just older mobile phones that are likely to be affected.
Experts warn many so-called smart devices, such as vehicle monitors, security systems and e-readers, could also be hit.
Some 4G parallel imported phones that don’t support the "VoLTE" technology used by Spark, One NZ and 2degrees for voice calling could also stop working.
In 2025, One New Zealand completed 258 mobile upgrades, with every One NZ mobile site now equipped with 4G technology, including a large portion with 5G, Byrne said.
“The good news is most customers are already on 4G and 5G, but if you or someone in your whānau is still using a phone that relies on 3G for calling, now’s the time to upgrade. Dunedin switches off 3G from tomorrow with the rest of the country to follow by the end of March.”
New Zealanders on any mobile network can also free text 3G to 550 to check whether their phone will work on One NZ’s 4G and 5G networks.
Spark said the most common 3G phones on its network were:
iPhone 6
Samsung Galaxy S7
Huawei Y5
HMD Global Nokia 3310
Huawei Nova 3e
Mobiwire SAS Pocket 2
Oppo A5 (AX5)
Samsung Galaxy J2 Pro
iPhone 5S
Alcatel 1B
- Allied Media
