I don’t have any user that I can ask about it

What's stopping you?

• 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 15.3.1

Go to Settings > General > Software Update.

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

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

Update using your computer -

Update iOS on iPhone - Apple Support

Here are some helpful articles that can guide you on how to free up storage space on your phone.

How to check the storage on your iPhone, iPad, and iPod touch

How to check the storage on your iPhone, iPad, and iPod touch - Apple Support

Manage your photo and video storage

Manage your photo and video storage - Apple Support

Clear Other storage on your iPhone or iPad

Clear Other storage on your iPhone or iPad - Apple Support

Do you mean upgrade to a newer phone? If so, go ahead and trade in your phone for a new one.

If you mean update your phone to a newer iOS version, start here: Update your iPhone, iPad, or iPod touch - Apple Support