This is a tough one. I have tried with squads but spoke with the VAPI team and this is not too reliable. You can use multi with English Spanish with Deepgram multi setting. You can also use OpenAI Realtime (still in beta) and it should work well but its not production ready. It's really a matter of switching both transcriber and many times the voice being used. I have been advised to have 2 numbers one for Language 1 and another for Language 2 for the best performance currently.