Voice isolation not working with Phone call

Voice isolation will work only with FaceTime --> During a FaceTime call, open Control Center, tap Mic Mode, then select Wide Spectrum.

These solutions have proven effective for me:

A1: Disable and enable Voice Isolation during phone calls 

If Voice Isolation fails to block ambient noise on your iPhone, a simple resolve is to disable the feature and enable it again during an ongoing phone call.

1. Access the Control Center on your iPhone. 
2. Tap Mic Mode and select any of the two options, Standard or Wide Spectrum. 
3. Exit the interface and wait for a few seconds. 
4. Access the Mic Mode menu again and choose Voice Isolation.

A2: Force Quit the app

Voice isolation on iPhone uses artificial intelligence to filter out background noise during calls. This facilitates clear and focused communication. However, at times, a few in-app glitches and errors tend to tamper this advanced feature. 

In such cases, forcing the app to quit can be an effective solution. 

1. Swipe up from the bottom of the screen and pause in the middle until the app switcher appears. 
2. For an iPhone with a home button, double tap the Home button to access App Switcher. 
3. Now, swipe left or right to locate the problematic app. 
4. Swipe up the app to close it completely. 
5. Now wait for a few moments. 
6. Relaunch the app after a while. 

This action will reset any temporary issues and potentially restore proper voice isolation functionality.