how to update ios 14.8

• 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 or newer, you can update to 14.8 or 15.0.2

Go to Settings > General > Software Update.

If that doesn't work,

Can you post a screenshot, it could reveal why you aren't able to update.

Make sure you:

• Are using a WiFi connection (not a hotspot).

• Have your battery charged at least 50%. Better yet, keep it plugged in during the update.

• Are not using a VPN connection.

• Do not have power save mode turned on.

• Do not have a beta version installed.

• You have at least 6 gigs of storage available.

You can also check out this article for help -

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

https://support.apple.com/en-gb/HT201435

Which exact model is your iPhone? If it is a newer model than an iPhone 6 or 6 Plus, it can be upgraded to the latest version of iOS 15.x ... currently 15.0.2.