Change setting update IOS from wifi to data cellular

You have to just turn OFF the Wi-Fi Setting OR be connected to your cellular network, which you already are.

You need 5G service on your iPhone to install an iOS update over a cellular network. Only iPhone 12 and newer models have 5G capability.

You have an iPhon 8 with LTE cellular service (5G is not available on an iPhone 8) and therefore you will have to update your iPhone over a Wi-Fi Network.

Make sure that your iPhone is setup to meet the following requirements before you attempt to update the iOS version over a Wi-Fi Network. Open Settings ➡️ General ➡️ Software Update: If there is an update available for your iPhone then it will be listed here. Follow the on-screen instructions to download and update your iPhone. 

• Your iPhone must have a fast Wi-Fi connection; you cannot update over cellular data or a cellular hotspot
• The iPhone can not be in Low Power mode
• The battery state of charge must be above 50%
• Your iPhone must have at least 6GB or more free storage space
• Your iPhone cannot be connected through VPN
• You should leave the phone plugged in until it finishes updating, both to assure that it remains above 50% and to keep Wi-Fi enabled (Wi-Fi turns off when the phone sleeps if not connected to power).

Axel F.

No. This is because there is no such setting. Your iPhone will use cellular data if there is no Wi-Fi or if the iPhone is not connected to a Wi-Fi Network.

The thing to note is that you cannot perform any iOS updates over a cellular network with your iPhone 8. You must be connected to a Wi-Fi Network to download and complete the iOS update installation.

You may also 👉 update your iPhone by connecting it to a computer and then updating it. The computer, in this case, must have internet access.

Axel F.