Updatedting my iphone

Update your iPhone, iPad, or iPod touch

• If you have an iPhone 5S or 6/6plus, the highest you can update to is 12.5.5

• If you have an iPhone 6S through 13, you can update to 15.4

Go to Settings > General > Software Update.

Update your iPhone, iPad, or iPod touch using WiFi -

Update your iPhone, iPad, or iPod touch - Apple<https://support.apple.com/en-us/HT204204>

Support<https://support.apple.com/en-us/HT204204>

Update using your computer -

Update iOS on iPhone - Apple Support<https://support.apple.com/guide/iphone/update-ios-iph3e504502/ios>

You offered this poster very useful information! This is what I would have told him/her as well =)