Bluetooth phone quality bad

Hope someone can help me. I have connected my iPhone X to my Prius. When I make or receive a call the call volume is extremely low and the call breaks up even tho I have good reception. I have increased the call volumes in settings to Max but it’s making no difference. Also when I have an incoming call it shows on the Touch to go screen but there’s no ringing sound. Anyone have a solution please.

Many thanks

Martin