The Unwanted Interruption
Apple’s ecosystem is heavily integrated through a feature called Continuity. One aspect of Continuity allows your Mac to ring simultaneously with your iPhone whenever you receive a cellular or FaceTime call. If you happen to be working on your Mac, clicking the notification (or sometimes simply having the Mac awake) can automatically launch the FaceTime application and commandeer your webcam and microphone. While this hand-off is useful for personal setups, it is a privacy nightmare in a corporate environment. Having FaceTime automatically launch on a projector during a presentation just because your iPhone received a call in your pocket is highly unprofessional.
Disabling Calls from iPhone on Mac
To stop macOS from automatically starting FaceTime and ringing on your computer when your iPhone receives a call, you must sever the specific Continuity link between the two devices within the FaceTime preferences.
Open the FaceTime application on your Mac (you can find it in the Applications folder or via Spotlight search). You must be signed into your Apple ID to change these settings. Once the app is open, click on the word FaceTime in the top menu bar (next to the Apple logo) and select Settings… (or Preferences). Under the General tab, look towards the middle of the window for a checkbox labeled Calls from iPhone. Uncheck this box. The change takes effect immediately. Your Mac will no longer act as a receiver for your cellular or FaceTime calls, ensuring that the FaceTime app remains closed and your workflow uninterrupted, regardless of activity on your paired iPhone.