How should I update my iphone without another phone

You need about 6 GB device storage and good Service and/or Wi-Fi.

If they are On, turn Off Hotspot & VPN.

Charge the battery > 70%.

See the following Apple articles:

Update your iPhone, iPad, or iPod touch

Update your iPhone, iPad, or iPod touch - Apple Support (IN)

If your iPhone, iPad or iPod touch won’t update

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

You can do the update via PC, see this Apple article: Update software on iPhone, iPad or iPod touch in iTunes on PC

Update software on iPhone, iPad or iPod touch in iTunes on PC – Apple Support (UK)

If you have a Mac see this Apple article: Update your iPhone, iPad, or iPod touch with the Finder

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

Which iPhone do you have? Which iOS version are you using on that iPhone?

Are you asking about how to update your iPhone without joining a Wi-Fi Network? If yes, then you will need an iPhone 12 or iPhone 13 or iPhone 14 with 5G service and then you can update over the cellular network. If you do not have 5G service then you can update your iPhone by 👉 connecting it to a computer and then updating it.

Axel F.