On settings>general setting menu on my iphone x i can not find software update selection, how can i update my IOS

Are you following these instructions?

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

The support article states that if you can’t find the update on your device, to use a computer to update.

If you can't see the update on your device, use your computer to update your device manually. Learn how to update your device manually if you're using a Mac with macOS Catalina or later, or if you're using a Mac with macOS Mojave or earlier or a Windows PC.

try and update your iOS via a Mac or pc instead

Update your iPhone using a Mac with macOS Catalina or higher

On a Mac with macOS Catalina or higher, you will use the finder in order to upgrade your iPhone. Make sure to Back up your device before starting the upgrade process.

On a Mac with macOS Catalina or later, you will follow the following steps:

1. Open a finder window
2. Connect your device to your Mac via a lighting to usb A or a lightning to usb c cable
3. Select your device in the left sidebar of the finder window
4. click general, then click check for update
5. Click download and update.
6. If asked, enter your iPhone passcode

Update your iPhone via a Mac running macOS Mojave or earlier, or on a Windows PC

On macOS Mojave or earlier, or on a windows machine, we won't use the Finder to upgrade your iOS

Instead, we will use iTunes. Make sure to Back up your device before doing any update or upgrade to your phone.

1. Open iTunes
2. connect your device to the computer with an lightning to usb a or a lightning to usb c cable
3. Click device button in the iTunes toolbar
4. In the summary tab, click check for update
5. Click download and update, follow The on screen instructions
6. If asked, enter your iPhone passcode.

If you don't have a computer handy, try a Forced Restart on the iPhone to see if that might help.

Force restart iPhone - Apple Support

If still no luck, it is possible that you have a phone that was provided by your employer? Depending on how the iPhone was set up by the IT Admin, software updates might not appear on the phone.

fowahed wrote:

Thank you! I managed to update using a computer but unfortunately, I'm failing to activate my iPhone since it is second-hand and I can not find the contacts of the previous owner. How can I get out of this?

There is no way around needing the previous owner’s help. They will need to remove activation lock. If you can’t get in touch with them, there is nothing that you can do now.

I'm failing to activate my iPhone since it is second-hand and I can not find the contacts of the previous owner. How can I get out of this?

The only way out of this is to get the original owner to remove the activation lock on the phone. To put it bluntly, the phone is useless until this occurs.

You’ve encountered activation lock. That’s an anti-theft feature designed to make it useless to anyone other then the owner of the account used to lock it.