If you try to enable Siri but still goes to voice control when trying to access Siri, you probably forgot to select language for Siri. If you dont select any language for Siri, Siri will just deactivate once you leave the Siri settings. And when trying to use Siri, you will only get Voice Control when holding in the home button.
So if your Siri language is empty, click to select a language, and Siri will work just fine.
Happy Siri!