In car bluetooth call waiting problem.

While on a current call in car when connected via in car bluetooth , i receive a 2nd incoming call, i briefly see the phone options screen and the caller is then diverted to busy tone, i don't get chance choose hold call & answer or end call & answer.

When not connected via bluetooth, call waiting waiting works fine and gives me the option to ignore incoming call or hold first call and answer 2nd call.

Vehicle is Renault Trafic model connection via in car bluetooth. same problem phone worked fine in previous Renault Trafic model. i can't find any settings in car system that solve the problem.