Why does '41004' appear in the iPhone carrier section after updating my iOS?

Zong is not an official iPhone carrier. In fact the iPhone is not available for sale in the country where that carrier operates.

That is probably why you are not getting the name of the carrier on your phone.

Ok. Try reaching out to your carrier and ask them. I think this is carrier related. Let us know what you find.

Hello!

What iOS version are you currently on?

Related: iPhone 13 carrier name changed to '41004'… - Apple Community

What carrier are you using?

Good to know. Thanks