I phone 11 pro connecting to car phone ( audi a7) locking up

recently connected my new i phone 11 pro to my audi MMI and all connected fine. the problem is the phone when answering locks the MMI screen and no conversation can take place. The screen is locked and the music is muted as if in a call. The only way to clear the locked screen is to turn off the car and restart . i had an i phone 6 before and all ok. I tried the iphone 6 again and it works fine. Both phones have latest software 13.6 installed. tried deleting iphone 11 pro from the mmi and reconnecting but same result. any one had same issue and knows the fix?