The docs implies that there's no support for non-english locales but I can clearly search "something" on Gmail using Google Assistant. My understanding is that it translates my command to English and then executes it.
The main problem is that I want to "call" someone in my app but in Turkish "call" also means "search". So I can't use CREATE_CALL bult-in-intent... Any suggestions?
Also; I know Dialogflow allows developers to define other pronunciations for application name, is there anything similar in App Actions specifically?
With App Actions, each BII has different language support. You will need to consult the reference documentation for your chosen BII to find out what languages it supports. You can see from the CREATE_CALL docs that Turkish is not supported. In fact, current, Turkish is not supported by any BII.
The way voice is handled in Google applications is not necessarily any indication of how App Actions can work for your app. If you don't see it in the docs, then it's not supported.