Atlassian Team members are employees working across the company in a wide variety of roles.
April 4, 2018 edited
Hi, Carlo.
1-1 conversations will be exclusive between two users only, which means that you are not allowed to invite another user into the conversation.
Should there be any need to have a conversation for more than 3 users at a time, it will be best for you to create a room (private, if you need it to be specific to 3 users only via invite).
To create a room, please refer to the Chat in rooms documentation and let me know if you still run into any issues along the way.