upgrade

There are two ways to download, verify and install the update on your iPhone. You can do this over the air (OTA) by connecting to a Wi-Fi Network OR you can update manually using your computer. Learn how to update your device manually ➔ if you're using a Mac with macOS Catalina or later, or ➔ if you're using a Mac with macOS Mojave or earlier or a Windows PC.

Axel F.

Either go somewhere where you can use Wifi, or if you have a computer, update your phone on your computer in iTunes.

See this link if that's an option for you --> Update software on iPhone, iPad or iPod touch in iTunes on PC - Apple Support