I can’t update my iphone why??

Hi AtifAbdullah,

Thanks for posting in Apple Support Communities. It sounds like this happens when you're trying to install wirelessly. Right? In that case, we'd recommend using the guidance in If your iPhone or iPad won't update - Apple Support which should help. The following article may be particularly helpful.

"Remove and download the update again

If you still can't install the latest version of iOS or iPadOS, try downloading the update again:

1. Go to Settings > General > [Device name] Storage.
2. Find the update in the list of apps.
3. Tap the update, then tap Delete Update.
4. Go to Settings > General > Software Update and download the latest update.

If you don't see the update in the list of apps or if the issue happens again, you need to update your device with your computer:

• Update your device using a Mac with macOS Catalina or later
• Update your device using a Mac with macOS Mojave or earlier, or a Windows PC"

All the best.