We have built Krisp iOS app to fix this. Krisp is powered by our infamous Deep-Learning based noise-canceling technology.
The app is very simple, yet quite practical. You can join Zoom, Meet, Webex, etc meetings with a single touch and also call any phone number you want, without worrying about background noise.
Apparently getting access to the microphone stream during calls, even from your own app, is really tough. There is only one provider that we know that implements the concept of "advanced audio filters" and that's Twilio's Voice SDK for iOS.