We would like to set up a chat group for our help desk so any user could chat with them at any time. I don't think Teams has this functionality, or maybe I'm missing something or maybe there is an third party add-on for this.
As far as I can tell, when someone wants to start a Teams chat, they must choose the members of the chat individually, i.e. they can't choose to chat with an O365 group.
An org-wide team can't be used because every member of the organization would be notified of, and be able to see, every message that's posted.