How to update iPhone to latest iOS?

You can use cellular data if your iPhone has a 5G connection. That would mean that you would need to have an iPhone 12 or iPhone 13.....and.....your carrier is providing a 5G signal.

If you still have the iPhone 7 listed in your profile, you cannot update using a cellular signal.

To update over the air from the phone all of these requirements must be met:

• You need at least 6 GB of free storage
• You must be connected to a Wi-Fi network (and not a personal hotspot)
• The phone must be charged to at least 50%, and preferably plugged in so it stays above 50% during the update
• The phone must not be in Low Power Mode
• The phone must not be connected through VPN, and it may be necessary to delete any VPN apps and VPN profiles
• The phone cannot be in Airplane mode
• You cannot still have a beta version installed on the phone<—If Settings/General/Software Update says that you are up to date with a version of 14.x this is the cause
• You cannot have a previous version that was downloaded, but not installed - go to Settings/General/iPhone Storage to look; if you find an iOS installer, delete it

If you can't meet all of them you can still update using your computer.

No, you can't use cellular data to do an iOS update on an iPhone 7.

Update your iPhone, iPad, or iPod touch - Apple Support