Automatic voice change based on language with voice over.

I am Blind and using voiceover. When I get a message with text in Tamil, voiceover does not reading the Tamil text, while it read for other languages. All language and voice settings are properly configured. Happens in all messengers and apps. Have to manually change the voice to Vani. Cannot set Vani as default, since its English pronunciation is horrible. Please help to read automatically.