Some of the phone numbers from Google's Knowledge Graph cards are now linked and open Google Hangouts. When you search for a local business, Google usually displays the phone number next to the address. Click the phone number and you can call directly from your browser using Google Hangouts, which opens in a pop-up window and informs you about the fees. Calls made to the U.S. and Canada are free.
For searches like [john radcliffe hospital phone number], Google shows a separate card that includes the phone number.
It's interesting to notice that not all phone numbers are clickable. Phone numbers from local search results or from ads don't have links. Another exception: customer service numbers.
{ via Search Engine Roundtable }
