https://www.cnbc.com/2018/07/09/microsoft-challenges-slack-with-a-free-tier-for-teams.html

Microsoft announced on Thursday a free version of its Teams app, stepping up competition with chat service Slack.

Until now, Microsoft only provided Teams to clients that pay for Office 365 and its portfolio of subscription productivity apps. Slack has offered both free and premium options since its public launch in 2014.