If you plan or need to decide about the deployment of Teams with Phone System this session will be helpful for you. Knowing exactly how the Microsoft Phone System works you can potentially save some money or mitigate unpleasant surprises with capacity planning and not expected user experience. Real use cases and examples from deployments of Teams telephony not only in officies but also plants and other type of production in company with 30k+ users. In old times almost all people had telephone by default. So the planning usually calculates with 1 for 1 replacement of the phone with licensed user for Phone System. What we have seen over the last months is the fact that the amount of regular telephone calls are diminished by scheduled calls and virtual meetings or even by adhoc native Teams calls. So do I need to enable and license all my users with Phone System in order to give them option to answer the external PSTN calls? How is the Teams phone device licensed? Are there any limitations of Common Area Phones? What about Auto-attendant and Call Queues? When do I need to assign license to resource account? Is it the same Phone System license? Do I need to have Direct Routing or Calling Plan for my use case? Does dialing out from meeting mean I need to have Audio Conferncing? What if I have analog phones? When do I need to license my users for dialing out and is it the same for dialing out from meeting and which license then use? I will present during my session real use cases and scenarious which we have identified during deployments of Teams telephony in HeidelbergCement. I believe that you will leave the session with better understanding of how to define your personas for telephony usage which will help you properly plan your Teams telephony deployments.