It won’t be that easy and fast…
Most MNOs proceed to “reharvest” (as they so nicely call it) 3G and 2G frequencies, but keep their 3G networks. Even if they have been shouting that 3G sunset for years… One of the reasons: If you only have a 4G (or 5G) network, you have to use Voice-over-LTE if you still want to use your phone’s native dialer. Simply put, the native dialer then becomes a kind of SIP client that contacts SIP servers on the network (search for “IMS” that’s the exact name). The problem is that the apples and samsungs of this world want to checkout too… understand : you have to reach a commercial agreement with the big players otherwise they won’t open their native dialer for you. That is why the list of supported VOLTE handsets can be so different between different MNOs. No technical reasons, just commercial… And I’m not talking about the fair amount of dumb-phones or older smartphones that don’t support VoLTE….
So as an MNO you have a large cost to develop such an IMS network and on top of that an extra “commercial” cost. The big difference is with the upgrade to 4G, 5G, etc.. where you can capture extra revenues for the “extra speed”, that is much more difficult for VoLTE… Who is going to pay extra just to be able to call with native dialer, that’s what the phone has been doing for decades…
