After testing voice calls for the past few months, Slack is now opening up the feature to all of its workaholic users. It works as you'd expect: you can initiate calls with a new telephone icon in Slack's desktop offerings, or by clicking through a dropdown menu on its iOS and Android apps. Then you can chat with coworkers using your voice, just like olden times. Any Slack user will be able to make individual calls, and teams who pay for the service can also initiate group calls for any Slack channel or group chat.