Unlocked phone + skinny ~> not VoLTE ~> sad 4g

Forums › Spark New Zealand (including Skinny and BigPipe) › Unlocked phone + skinny ~> not VoLTE ~> sad 4g

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#3453294 15-Jan-2026 12:53

To clarify: all three main providers support voice over 4G, but they all use different technology to do it. Your existing phone apparently supports 2degrees' brand of 4G voice, but not Skinny's. It follows that using a 2degrees SIM will likely get it working.

This is a bit of an oversimplification but it hopefully gets the point across.

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#3453296 15-Jan-2026 12:58

Folks this is another prefect example why VoLTE (not 4G / LTE) is a cluster fish!! Just VoLTE

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#3453309 15-Jan-2026 13:26

@jfw01:

nitro:

swapping a 2D sim not an option for you? coverage in your area, perhaps?

I am confused. 3G is shutting down. Is there something from earlier than 3G that is permanently not shutting down?

He meant 2D as in 2Degrees.

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#3453311 15-Jan-2026 13:33

Do we need some sort of domestic VoLTE roaming to get around the problem with phones perhaps lol

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#3453312 15-Jan-2026 13:35

yitz:

Do we need some sort of domestic VoLTE roaming to get around the problem with phones perhaps lol

The problem is the phones not having the profiles needed when attached to one network or another. Nothing to do with the network communicating to each other.

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#3453320 15-Jan-2026 13:56

yitz:

Do we need some sort of domestic VoLTE roaming to get around the problem with phones perhaps lol

@yitz that will not do anything - The world just needs a single standard for VoLTE

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#3453330 15-Jan-2026 14:06

yitz:

Do we need some sort of domestic VoLTE roaming to get around the problem with phones perhaps lol

VoNR (5G Voice) should be better but you need widespread 5G SA (Standalone) so you don't get caught falling back to VOLTE (4G) which may fail......

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#3453337 15-Jan-2026 14:23

I mean roaming as in making it work like VoWiFi having it connect from externally (ePDG?) and zero rating data.

Surely no compatibility issues then?

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#3453345 15-Jan-2026 14:41

wellygary:

VoNR (5G Voice) should be better but you need widespread 5G SA (Standalone) so you don't get caught falling back to VOLTE (4G) which may fail......

I wouldn't bet on it. It's the exact same IMS core, which is where the complexity is. Just a different packet core (5GC vs. EPC). If anything it's likely to be even more hilariously hit and miss given how complicated 5GC is compared to EPC.

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#3453350 15-Jan-2026 15:28

freitasm:

The network shutdown was announced mid-2024 and you bought the phone in mid-2025. The retailer has some responsibility.

Would be interested to know how the OP gets on with this.

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#3454163 19-Jan-2026 11:56

jfw01:

So, what's the cheapest smartphone that offers me an actual choice of networks, and how could I have identified it in March 2025, before purchasing?

iphone.

Anything else you will be wanting to get from the network vendor to ensure compatibility with their network that they are responsible for ensuring is an ongoing thing.

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#3454170 19-Jan-2026 12:14

richms:

jfw01:

So, what's the cheapest smartphone that offers me an actual choice of networks, and how could I have identified it in March 2025, before purchasing?

iphone.

Anything else you will be wanting to get from the network vendor to ensure compatibility with their network that they are responsible for ensuring is an ongoing thing.

Correct. Android devices will be a bet. The most expensive ones will work. The mid-tier might and the cheap ones... Are too cheap.

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#3454176 19-Jan-2026 12:58

Classic telco walled garden 😞

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#3454188 19-Jan-2026 13:44

yitz:

Classic telco walled garden 😞

Not at all. 3GPP chose to build their VoIP service on top of SIP. The great thing about SIP is that there are about a thousand different ways you can accomplish a call scenario. The bad thing about SIP is that there are about a thousand ways you can accomplish a call scenario.

The old CS standards like ISUP and INAP/CAMEL were far more limited with little or no flexibility on what you had to do in the network to make such and such a call work - but that also makes interoperability pretty trivial.

I think I can speak for all networks when I say it'd be a lot less work for us if IMS Just Worked{TM) like circuit-switched does. We have plenty to be getting on with without having to figure out why the HappyPhone 9000 you bought for $2 from Temu won't make a voice call after 4:17pm on every even-numbered Tuesday.

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#3454233 19-Jan-2026 14:05

HappyPhone 9000 you bought for $2 from Temu won't make a voice call after 4:17pm on every even-numbered Tuesday

@SaltyNZ Can you please look into this issue for me? I just purchased one and this is happeing

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