We have a service desk portal to assist external customers by tracking and logging issues but when a few of them had attempted to gain access to our portals + Knowledge Base, us agents receive an email indicating that the new user has joined our project and is now consuming a seat on our license. This issue has occurred several times now with 2-3 different users.
Please let me know the cause of this issue as well as the steps to take so this issue does not present itself again.