In 2017 Microsoft released Teams as an integration with their Office 365 subscription productivity suite. Teams is Microsoft’s Unified Communications as a Service (UCaaS) platform, and will eventually fully replace Skype for Business Online. Teams allows users to collaborate via chat, video conference, and calling.
In order to use Microsoft Teams as a means to connect to the PSTN, an organization must enable Microsoft Phone System, which can be enabled on certain enterprise licenses. Once an organization enables Phone System, they then have two options for calling within Teams.