iOS 8 or later
macOS X Yosemite or later
The iPhone Cellular Calls feature allows you to make and receive cellular phone calls from your iPad, iPod touch, or Mac - without getting your iPhone out of your pocket - if they are on the same network as your iPhone.
It requires an iPhone running iOS 8.1 or later and an activated network plan and it will work with any iPad or iPod Touch running iOS 8 or later and any Mac running macOS X Yosemite or later.
To make a call on your Mac: Move the cursor over any phone number in Contacts, Calendar, Safari or other app that detects such data > Click the arrow in the box that outlines the phone number > Choose Call [phone number] Using iPhone. You can also open the FaceTime app and enter a phone number in the search field and call using the audio option.