Thank you for your reply @Ag.Steel
I have read the same, therefore I was trying to understand if there are any French telecom operator that would support VoLTE (and VoWifi) on any Sony XA2 after the 2G will be switched off.
Otherwise, I am wondering what to do (having a device potentially VoLTE but not “accepted” by the telcos is quite frustrating …)
Hopefully with 3G being shut down in 2028, we still have 2 working years from now, in France.
Perhaps I have misunderstood the whole subject then…
I thought that phone calls were either carried through 2G or VoLTE (4G) networks… so when 2G is shut down, if our phones are not VoLTE compatible, no possibility to make voice calls or send/receive SMS… this is why I was concerned about VoLTE ….
I was trying to read more on the subject, but I saw that the French articles are a little bit misleading … always mentioning that 2G phone will not work when 2G/3G are switched off (which I understand) and therefore pushing customers to buy smartphones VoLTE compatible, but never clear mentioning whether smartphones with 2G/3G/4G without VoLTE will be able to make calls and exchange SMS when the 2G is switched off, before the 3G is switched off as well. This is relevant, since in France, sunset dates are different, 3G surviving for a couple of years more.
Any hints?
Thank you in advance
i dont think that 2G/3G will works in time.
VoLTE is used from 4G or more , i dont know for 3G
3G will work without 2G. 3G calls and SMS are going to work as long as 3G is working. 3G is still circuit switched, so it is standard voice call. 4G is purely packet switched network without voice calls or SMS. Voice calls are more complex VoIP - VoLTE - part of IMS (IMS is whole suite of VoLTE, ViLTE (video), SMSoLTE, VoWiFi, VoNR (New Radio - 5G) etc
Sony have good support for IMS. My Sony Xperia 1 III and V do support it over LTE, NR and WiFi.
The ARCEP is clear, phones without VoLTE support (all phones without 4G and a few rare ones with 4G) will not be able to connect to the networks at all for anything, SMS, calls, internet.
The date changes depending on the network-provider/operator. As often, historical provider (Orange) is the worst and Free the best/most honest.
They tell people to check on their hardware specifications whether it supports VoLTE.
Thank you @wizard for this reply. That is the kind of answer I was not able to find in the telco websites or official channels.
perhaps I cannot find the answer to my question: in the period of time when 2G is switched off, but 3G is still active (2-3 years in France), are smartphone without VoLTE capable of calls or SMS?
I have the impression that there is a general lobby pushing to move to new smartphones VoLTE capable from day 1 to be future proof, whereas I feel there are old 3G smartphones that can do the job for some time before being recycled (or sent to the landfill 
I am always afraid this will be the way it will go with such a campaign …).
And reading how subtle activation of VoLTE can be for some smartphone models/carriers, I have the impression that the freedom of changing operator may be limited ….
It looks like 3G is perfectly fine to pass phone calls or send SMS, though you are right: it is not clearly said anywhere even though 3G will be available for 2-3 years more than 2G