Microphone not working when plugged to AUX on iPhone 15 Pro Max

I recently upgraded to an iphone 15 pro max. With my iphone 13, I used to have a lightning to AUX cable in my car which enables music/ sound to play the iphone through the speakers and enable me to take calls handsfree. I replaced this with a USB- C to AUX cable (to suit the iphone 15) and the music/ sound plays through the sound system fine, however the microphone no longer works (i.e. answer calls and person on the other side cannot hear me). It also has disabled Siri- if I say "hey Siri" this isn't recognised. Please help how to enable the microphone

[Re-Titled by Moderator]