[favsq]

Dumbphones are 4G. 4G voice service requires VoLTE but mobile operators have to whitelist phone models, the phone has to have the IMS in the internal database... all in all don't expect VoLTE to work. So voice downgrades to 3G. But 3G is being shut down by many operators and more to come. So voice downgrades to 2G, but 2G has a very low limit of concurrent calls, let's say a few dozen. So it's possible that your dumbphone won't work at all.

[tablespoon]

> But 3G is being shut down by many operators and more to come. So voice downgrades to 2G, but 2G has a very low limit of concurrent calls, let's say a few dozen. So it's possible that your dumbphone won't work at all.

2G is being shutdown too (IIRC, I had a 2G pay-as-you-go phone that stopped working years ago), and it would be surprising to me that a carrier would shutdown 3G before 2G.

https://en.wikipedia.org/wiki/GSM#Discontinuation

[favsq]

It makes sense because many specialised IoT appliances are 2G-only. At least that's the way it's happening in the EU. For example in Spain 3G will be phased out in 2025 while 2G will be phased out in 2030.

https://en.wikipedia.org/wiki/2G#Phase-out

https://en.wikipedia.org/wiki/3G#Phase_out

[jollyllama]

There's more to it than that. I had a model where voice would work on both networks but SMS would only work on one. The only contacts app you could use also relied on a proprietary gateway, and took a minute to open on the other network.

Also, updates to SMS implementations eventually broke SMS on the good network.