Do you want to try Microsoft Teams? You can now easily get Teams and evaluate some basic communication and collaboration features for up to 300 people. E.g. unlimited chat, search, 10 GB for storing your team data, 2 GB per person, audio/video meetings (P2P, multiparty), Office Online apps, third party apps and of course internal as well as external communication and collaboration.
For more details go and visit the Microsoft Teams Blog Post: https://techcommunity.microsoft.com/t5/Microsoft-Teams-Blog/Introducing-a-free-version-of-Microsoft-Teams/ba-p/214592