I want to update my iPhone
More details about iPhones
[Edited by Moderator]
Question marked as
Go to Settings > General > About
What does it say for iPhone Model and Software Version?
You need an iPhone 6s/6s Plus or newer in order to run iOS 15..
Supported iPhone models - Apple Support
If your iPhone is an iPhone 6/6 Plus, then you cannot upgrade beyond iOS 12
have you read thru this support article for updating?
Update your iPhone, iPad, or iPod touch - Apple Support
need more storage for update?
If you need more space for an update on your iPhone, iPad, or iPod touch - Apple Support
issues?
Updating iOS: common issues and solutions - Apple Community
video..