@BenRooke Quoting from the Meetings First article:
At minimum, users must be licensed for Teams. In addition, they can be licensed for Audio Conferencing, if needed.
This could be satisfied by assigning an Office 365 E3 license and the Audio Conferencing add-on. Alternately, if the user has an Office 365 E5 license, Audio Conferencing is included with that SKU, so only the one license is needed.
Just so it's clear, "Audio Conferencing" refers to the capability of hosting a Teams meeting that participants can join by dialling in from the PSTN. If participants are only joining with the Teams client, then Audio Conferencing is not needed.
