First, check that your phone supports 4G/VoLTE on your local network. The mobile networks have lists of supported makes and models of phones here:

• Use this 2degrees tool to check your phone’s IMEI number for 4G and VoLTE compatibility. Here is a 2degrees compatible mobile list.

• One NZ list of supported mobile phones.

• Spark NZ tool with instructions to check your phone’s IMEI number to check 4G, VoLTE and emergency calling compatibility

The Spark NZ tool in this list is useful because it also provides an indication of whether the phone uses 4G and VoLTE for emergency calls. Some older 4G capable devices were configured to use 3G networks for emergency calling. This is important information to know before an emergency!

(If your mobile plan is with a local company other than the above three, that company will use one of these three mobile network operators. You can check which mobile companies run on which networks here.)

Even if your model of mobile phone is listed as supporting 4G and VoLTE on local networks, it is still worthwhile to test it yourself to confirm whether you can make a voice call using 4G. This is because there are a number of other factors that might need to be considered.

Note: it is important that you DO NOT test 4G with VoLTE calling compatibility on your phone by dialling emergency services as this will interfere with real emergency calls!

If your phone displays that you are connected to 4G on the status bar on your phone then you could simply try phoning a friend using the mobile phone’s call functionality (i.e., do not use apps like Messenger or WhatsApp to call as these may use data over 4G but do not use the VoLTE standard). Once the call is connected, different phones may show different indications that it is using VoLTE. Here is a list of indicators from Mercury that your current call is using 4G and VoLTE:

You can see if the call you are making is a 3G or 4G call by checking the following:
* Apple iPhone: The 4G icon will remain in the status bar.
* Samsung: HD calling appears while placing a call. HD also appears in the call screen during the call.
* Huawei: HD appears if the call is connected or has gone to voicemail. No icons appear while the phone is ringing.
* OPPO: VoLTE appears in the status bar.
* Nokia: VoLTE appears in the status bar after pulling down the notifications menu.
If you don’t see these icons, the call is most likely using standard 3G (HD Voice).

If you are unsure, another option is to use Hugh Jeffreys’ iTest app, which you can download for a small fee. It runs multiple mobile phone device tests including testing whether your phone supports VoLTE calling.

If your phone passes these checks, you can have a good degree of confidence that your phone will be able to make regular calls after the 3G closedown. However, it is also important to note that some older phones may use 4G/VoLTE for normal calls but that model of phone may enforce use of 3G networks for emergency calls. Juha Saarinen wrote the following explanation for this in March 2024:

“Further technical information received on the reason why some 4G handsets switch to 3G for emergency calls say this is how the older 3GPP Release 8 standard handled them. The standard was “frozen” in 2008, and meant that emergency calls to 111 in New Zealand […] were forced to 3G. Release 8 devices are often older than 8 years by now.”

James Parker, an Australian IT and Networking specialist, has noted that 4G phones with VoLTE that use 3G for emergency calling do not have that setting “hard-wired” on the phones, but is a matter of software configuration. Note that the Spark NZ tool includes information about whether your phone will use 4G/VoLTE for emergency calling but as VoLTE configurations may differ among mobile networks there has not been a guarantee of VoLTE support across all networks. So, if in doubt, check with your mobile company.

If your test call is unsuccessful, then here are some further potential issues that 2degrees have identified, though these could similarly apply to the other networks

Check the 4G network coverage claims from your mobile provider, which are compiled on this page.

Here are some instructions if you are using an Android device. Here are instructions to install updates on your iPhone.

The following instructions to remedy this are from One NZ:

Then check that 4G/5G data is enabled in your phone settings as well as 4G voice calling/VoLTE.

Head to your mobile network settings and switch the 4G/VoLTE calling toggle to “On”

For Android phones: Go to Settings > Connections > Mobile networks > VoLTE calls enabled

For iPhone (iOS) This is usually already enabled for most iPhones: Go to Settings > Mobile > Mobile Data Options > Voice & Data (ensure 4G or 5G is “On”)

Check with your mobile phone operator if you suspect this. However, the New Zealand Telecommunications Forum states that “If your old SIM card fits into the new devices’ SIM card slot, then you are sorted.” This suggests that all nano sim cards should be OK.

Your phone needs to be able to use the same frequencies for communication as local mobile networks.

• See One NZ frequencies here: What are the mobile network frequencies used by One NZ?.

  • See Spark NZ frequencies at the bottom of this site: Spark NZ network coverage. (If you use Spark, then you can check mobile compatibility with their 4G compatibility tool.)

  • 2degrees is here: 2degrees | Powertec Information Portal.

  • Another online phone/network compatibility checker tool is available here: FrequencyCheck – Mobile Network Compatibility Search for Unlocked Phones and Devices (but there are no guarantees as to the accuracy of the information).