How do I update my iPhone 7 iOS?

This may heklp --> Cannot update iOS - Apple Community

Hello,

There are different ways to ensure the highest iOS that your device will support is installed on your device. When updating, your device will update to the highest version currently available that it will support, or it will just say it is up to date (and can't go any higher) and won't install anything. If you want to run a higher system version than your current device is capable of running, you need to buy a newer device.

iPhones 6S through 7, and SE(gen. 1), will only update to iOS 15.8.3 If you aren't already running that version you can update to it.

This support article has instructions about updating an iPhone or iPad wirelessly --> Update your iPhone or iPad - Apple Support Read the article for recommended criteria for being able to use wireless updating.

You can also use Mac and PC computers to update system software --> Update iOS on iPhone - Apple Support

Your tag line indicates that your iPhone 7 is running iOS 15. You can update an iPhone 7 to the latest release of iOS 15 – currently iOS 15.8.3.

About iOS 15 Updates - Apple Support

You cannot update an iPhone 7 to iOS 16 or higher.