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I have the Sony xz and it's not showing wifi calling for vodafone
You need their ROM. Basically you need to install their own operating system on the phone. Then it will show up.
Same here (Provider: o2). According to O2 support they don't have a custom ROM for this model, and it is also listed on their website as one of the phones supporting WLAN call. Nevertheless the WLAN call menu doesn't show up anywhere.
Stuck for days with this topic now.
Resolved this issue a while ago, and forgot to publish the solution.
The reason for the missing menus was that I had been sold a "grey import" phone with Belgian firmware and all settings set to "Germany". I used flashtool and put in the correct "Geman Retail" firmware, also named "Customized DE" and gee, Wifi calling was accessible right away.
Others having this problem please note, that there are three firmwares for Germany: one for Telekom customers, one for Vodafone customers and another one for the "rest" of the providers.
You can check your firmware by dialing #*#*7378423*#*#, check the "customization number". The one you need is one of these:
1305-9090 Germany Customized DE
1305-4974 Germany Telekom.de DE
1305-7753 Germany Vodafone DE
Please do also note that for Wifi calling to work the phone must have a quite good WLan connection, if signal strength is too low (something around -75 dB, unfortunately the exact threshold seems to be undocumented) Wifi calling will turn itself silently off (though the switch in settings remains "on"). Other network services which are less quality demanding may continue to work without problems.
Greetz, Armin.