iphone se 2020 CAR ISSUE

I have the new iPhone se 2020. it Pairs and connects fine to my Audi... can play music as before and Waze app works fine. if I call certain people with iPhones through the bluetooth it becomes a distorted crackle. can call land lines fine and other phones and use car speakers no problem. If I switch the speaker from the car option to the speaker on the phone then fine when the crackling / distorted sound starts.... Software is up to date and previous iPhone was fine with car. have tried forgetting bluetooth device and repairing.... Any ideas or help would be appreciated as its driving me mad!!!