Thank you for asking a great question VICWEI62. Knowing all about your phone update is important. Your security is our number 1 priority. I'll be happy to help and clarify. I am not aware of any fraudulent carrier settings update. If the prompt is not coming from the phone system pop up, then it's not a carrier update.
When a carrier setting update is available, you'll just be prompted to install it on your screen. You can manually check it as well. Here's the details: https://support.apple.com/en-us/HT201270.
Just curious, what does your carrier settings update look like (screenshot)?
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