Type (or copy/paste) the phone number, and either press Enter or double-click the highlighted number.
OR hover over the contact picture and use the phone icon
NOTE: This option will automatically call the last number you used for that contact (i.e. Lync call, work number, mobile number etc).
OR to reveal a list of available numbers for the contact select the arrow next to the phone icon.
If you would like to leave one of your contacts a voicemail without disturbing them select the “Voicemail” option.
Once the call is initiated a call window will open: