For Xiaomi:
To unlock VoLTE: open your phone app and dial *#*#86583#*#*
To unlock VoWifi: open your phone app and dial *#*#869434#*#*
Now go into Settings > Sim Cards & Mobile Networks. You will see an option called "VoLTE enabled". Tap the switch to enable it. Scroll down further and you will see another option called "Make calls using Wi-Fi". Tap the switch to enable it. You can then choose whether the phone should prefer network or wifi right below.
VOLTE on non officially supported devices
Feb 7 2022, 03:23 PM
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