Software Update
How to update software using mobile data?
iPhone 6, iOS 12
How to update software using mobile data?
iPhone 6, iOS 12
Plug your device into power and connect to the Internet with Wi-Fi.
For using Mobile data, which is scarce and very expensive in many countries. is still not available for even large size app downloads leave alone iOS update.
You can not update iOS using cellular data. WiFi is required.
If you don't have access to WiFi, then you can use iTunes from your computer provided your computer has an Internet connection.
Software Update