I need help with the standalone sound function.

Greetings, my car only has CarPlay and doesn't have Android Auto. I can connect my S25U without Bluetooth problems. But when I get a phone call, the music stops, and only the call is heard. I have tried to set up the standalone audio function in several ways but failed. The call is still heard in the car, and the music stops. I need the music to continue, and the call to be heard on the phone. Is there a way to do that?