Why i cant show live voicemail in my call settings, my phone is iphone 11 pro max?

Hello erion02,

To complement @LD150 answer and in case you missed it in the document you looked at :

Live Voicemail is available only in English in the United States and Canada, excluding Guam, Puerto Rico, and the U.S. Virgin Islands.

That is provided by your cellular company - ask them if they do it.