Iphone 11 max pro Bluetooth crackling and not connecting

I have an iPhone 11 max pro and when I connect it to my cars hands free Bluetooth it make a static / crackling sound when the person on the other end speaks.

Ive contacted customer service on several occasions and have tried everything, they now say I need to update the car’s firmware??

My car works fine with iPhone 6, 7 & 8plus but not the 11max pro.

I have a pair of Bluetooth plantronics backbeat head phones and the phone struggles to find them and I need to turn Bluetooth off and on repeatedly until they connect. I’m so over the phone and tempted to go back to a iPhone 8 Plus :(