You can switch on Wi-fi calling in the settings:

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To switch on Wifi calling:

From the Main Menu

> Scroll to the bottom

> Tap Other Options

> Tap Advanced

> Scroll to the bottom

> Tap Continue

> Tap Yes

> Tap Open Network & Internet

> Tap Mobile Network

> Tap the option you see (likely Lebara)

> Confirm VoLTE is on (if slider is to the right, it is on. It is usually switched on by default)

> Tap Advanced

> Tap slider to the right of "Use Wi-Fi calling" to confirm on

> Tap Calling Preference

> Select whether you would prefer to prioritise Wi-Fi or Cellular Calling as you like

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