my i phone will not update to ios 16

Hi bellaharrison0109,

Welcome to Apple Support Communities. Are you trying to update your iPhone over Wi-Fi? If so, the steps in this article can help you with that:

If your iPhone or iPad won't update - Apple Support

Also, if you have access to a Mac or Windows PC with iTunes installed, you can use the computer to get updated. For a Mac with macOS Catalina or later follow these steps:

"Update your iPhone, iPad, or iPod touch using your computer

1. Open a Finder window on a Mac with macOS Catalina or later.
2. Connect your device to your computer.
3. Select your device in the left sidebar of the Finder window. Learn what to do if you don't see your device.
4. Click General, then click Check for Update. 
5. Click Download and Update. Continue by following the onscreen instructions.
6. If asked, enter your passcode. Learn what to do if you don't know your passcode."

Complete info can be found here: Update your iPhone, iPad, or iPod touch with the Finder - Apple Support

If you are using a Mac with macOS Mojave or earlier or a Windows PC, the steps needed are as follows:

"Update your iPhone, iPad, or iPod touch using iTunes

1. Open iTunes on your Mac with macOS Mojave or earlier or on your Windows PC.
2. Connect your device to your computer.
3. Click the device button in iTunes toolbar. If you don't see your device, learn what to do.
4. In the Summary tab, click Check for Update.
5. Click Download and Update. Continue by following the onscreen instructions.
6. If asked, enter your passcode. If you don't know your passcode, learn what to do."

Further info is listed here: Update your iPhone, iPad, or iPod touch with iTunes - Apple Support

Feel free to reach back out if you have any questions.

We hope this helps you.