I have Iphone 6 that is running on IOS 11.1.2 which is the latest version.
I have WhatsApp 2.17.81 version which also seems to be the latest.
The problem is that for Audio calls, the moment i switch on the speaker, my mic gets off and hence the callled party cannot hear me. It works well if my speaker is off though.
On Video calls, since speaker is on by default, my mic doesn't work.
I emailed it to whatsapp support team and this is what they have to say:
Sorry for the inconvenience. We are aware of the issue and we are working on fixing it in a future update of WhatsApp. Unfortunately, we can't comment on any future release dates at this time.
If you have any other questions or concerns, please feel free to contact us. We would be happy to help!
WhatsApp Support Team"