WLAN CALL in SFOS?

[emva]

This function is called VoWiFi and is currentry not supported in SFOS.

See also:
VoWIFI support in SfOS

Beta VoLTE on the Xperia 10 III, disabled by default

You are not exactly on topic… but the answer is that you can’t. There appears to be no plans for the older devices.