How to update iPhone to latest iOS?

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.

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.

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