This is too complicated I think. Why don't you simply use a call recording app for your device? I've been using this call recorder for several months to record interviews and it's much easier than the solution you offer. Or do you mean that such call recording will be free and at the same time crystal clear?
I'm using this call recorder, the Mac version records Zoom meetings as well as WhatsApp, Viber, Skype and other calls. I recommend you to take a look at the app, it's worth a try and video call recording is pretty easy.
As far as I know, automatic call recording on iPhone is impossible due to OS limitations. All call recording apps that I used on my iPhone recorded calls through the 3-way calling (i.e. that you need to merge calls before every call). The apps that promise automatic call recording on iPhone simply don't work... If call recording through a 3-way calling is ok for you, I'd recommend this call recorder for iPhone, it's the best app I've ever used for this purpose.
When it comes to call recording on iPhone, it's better to install the app that offers a notification that the call is being recorded (if you're worried about privacy violation). As far as I know, automatic call recording is impossible on an iphone due to OS restrictions (jailbreaking the device that you don't own is illegal), so call recording through a service number is the most popular option. My friend uses this call recording app for business needs and he says that it's pretty good, I never used it but heard that the recording quality is fine.. So you can at least try it))
Hey! I'm not sure if any free apps for call recording exist on iPhone. I'm using REKK on my iPhone X to record calls from my customers. Though it's not free, I like this app because it's easy to use, has a minimalistic design, and works without bugs. Plus, it converts all calls to text it's pretty good for educational purposes too.