If you see Add Wi-Fi Calling For Other Devices: Turn it on.
This option allows calls using your other Apple devices that are on the same Wi-Fi network as your iPhone.
After you turn on Wi-Fi Calling on your iPhone, turn on Calls from iPhone on your Mac. If you’re not asked to do so when you open FaceTime on your Mac, you can use FaceTime settings to turn on the feature.
In the FaceTime app Make and receive RTT calls in FaceTime on Mac