In the case where Skype for Business or CCE is deployed on-premise for PSTN dialling capabilities, its important to know the current limitations of deploying Microsoft Teams. A list of calling plan and audio conferencing availability by countries can be found in this website:

For places where PSTN Calling Plans are still not available, an on-premise deployment of Skype for Business or Cloud Connector Edition (CCE) are two options that are still required to leverage on-premise PSTN infrastructure for dial in/out to PSTN numbers. Everything about Teams has been built from the cloud-up, and thus deploying it is also much simpler than deploying a full Skype for Business on-premise infrastructure. On the other hand, Teams is completely cloud based and there are no plans to introduce an on-premise Teams server. Before jumping ahead on how to get Teams deployed, its important to note that Microsoft is still committed to Skype for Business Server and a new version of the on-premise server is targeted for release in the second half of calendar year 2018. Many organizations have also deployed Skype for Business in their environment and as they begin to transition over to Microsoft Teams over the coming months, there are several aspects that should be noted by IT administrators.

Multi chat client that includes skype