Recording Audio from iPhone (whatsapp) via quicktime on Macbook Pro

I'm using an iPhone SE (latest software) and a macbookpro (10.14.6).

I want to be able to record audio interviews conducted through WhatsApp voice (a free way to do international interviews). I have an app that syncs for phone calls made with the phone itself (tapatalk), but that app doesn't work with WhatsApp. I found a link that describes what I want to do and everything works except, I don't get any sound (which defeats the purpose): https://gadgets.ndtv.com/how-to/features/record-whatsapp-call-iphone-android-on-android-video-how-to-ios-1985089

When I start the recording (whether I choose movie, screen recording, or audio) I get no sound. And oddly when I test using the phone (not WhatsApp) to simply call my office, let it ring, voicemail starts, then I hang up--the screenrecording of this stops recording during the part when the office phone rings and the external voicemail message plays. There is screenrecording for that shows me dialing and shows me hanging up but nothing in between.

The audio works when I open a youtube video (although I can't hear anything through the phone or the computer during that recording but I see the recording levels and I hear audio when I playback).

So, any tips about getting around this problem so I can (A) hear the audio through the phone and (B) actually get audio from WhatsApp? Thanks in advance for the help.