Even I update to the latest version I still have that message, requesting to update, and it show error on the cellular

yaumin Said:

"Even I update to the latest version I still have that message, requesting to update, and it show error on the cellular"

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Two Things:

A. Try Another Update:

Update Using a Computer:

Have a Computer Handy? If so, try using a computer to update. Go here: Update your iPhone Using a Computer - User Tip

If of no success...

B. Whom to Contact:

Contact your Carrier, as the are the one who provide you with the service of Cellular.

yaumin Said:

"Even I update to the latest version I still have that message, requesting to update, and it show error on the cellular”

Q1. "[...]So I update it through laptop“

A1. Then you’re all set. Correct,

Q2. "for the carrie, the SIM card is used on iPad and other iPhone and it works. Could it be somewhere problem within the iPhone itself ? since modem firmware is missing.”

A2.Do you have any Security Software installed? And another thought is maybe it’s some setting in Screen Time.

Updating your iOS and updating your carrier settings are two completely different things.

Look here to update your carrier settings.

https://support.apple.com/en-us/HT201270

Talk to your carrier and see what they say, they might have seen this issue before and know how to fix it. If they don't, take it to an Apple store and have them check out your phone.

Try putting your iPhone in recovery mode and restoring it using your computer.