How do I update my iPhone 7 Plus iOS to 15.1

iOS 15.1 hasn't existed for some time. If your tag line is correct and you own an iPhone 7, it can be updated to iOS 15.8.3. If you have skipped a lot of updates, which if you are on iOS 14, you'll find success by connecting your iPhone to your computer and use either iTunes (Windows) or Finder (Mac with MacOS Catalina or higher) to update your phone.

See the following links:

Update your iPhone, iPad, or iPod touch with the Finder - Apple Support

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

Make sure that your iPhone is setup to meet the following requirements before you attempt to update the iOS version over a Wi-Fi Network. Open Settings ➡️ General ➡️ Software Update: If there is an update available for your iPhone then it will be listed here. Follow the on-screen instructions to download and update your iPhone. 

• Your iPhone must have a fast Wi-Fi connection . You cannot update over a cellular connection or a cellular hotspot
• Ensure that you do not have a beta updates activated in Settings ➡️ General ➡️ Software Update
• The iPhone can not be in Low Power mode
• The battery state of charge must be above 50%
• Your iPhone must have at least 10GB or more free storage space
• Your iPhone cannot be connected through VPN
• You should leave the phone plugged in until it finishes updating, both to assure that it remains above 50% and to keep Wi-Fi enabled (Wi-Fi turns off when the phone sleeps if not connected to power).

Axel F.

You can update an iPhone 7 Plus to the latest release of iOS 15.

About iOS 15 Updates - Apple Support

Update your iPhone or iPad - Apple Support

Updating iOS: common issues and solutions - Apple Community

Go to settings - general - software update and start there.

Apple's no longer signing 15.1. To install 15.8.3, use a computer or the Software Update function in Settings.

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