Internal mic still on when using headset
I have recently started having this problem on my iPhone11pro
When I am on a call using a headset (standard Apple lightning headset) and my phone is in my pocket, people I am calling say they hear lots of noise. If I take the phone out of my pocket, the noise go away (so they tell me).
It is as if the iPhone's internal mic is still on even when I'm using the headset (and the headset mic is working too).
Is there a setting somewhere that I might have chanced accidentally to cause this ?