How do I update my iPhone using mobile data

To perform an update procedure wirelessly, you need to connect your device to a reliable and fast Wi-Fi Network with internet access (no cellular data, unless you use a 5G network, no personal hotspot on your device, no VPN connections, no low power mode are admitted). AND I suggest that you keep the device plugged into power during the whole update process.

-- credit: ProustGiulio ASC