Provision VoLTE via Carrier Network Settings

1. Contact your mobile carrier's customer support and request that they 'provision' or 'activate' VoLTE (Voice over LTE) for your specific Fairphone IMEI number.

2. Once confirmed by your carrier, navigate to Settings > Network and internet > SIMs on your device.

3. Toggle the '4G Calling' or 'VoLTE' switch to the 'ON' position.

4. Restart your device to apply the new network configuration.

5. Verify the fix by dialing *#*#4636#*#*, selecting 'Phone information', tapping the three-dot menu, and confirming that 'IMS Status' now displays 'Registered'.