Adding unlimited users to private repo

I’m an admin on a private repo in an organization of which I am not a member. I’m under the impression I can add unlimited collaborators for access to the repo because of this: GitHub is now free for teams - The GitHub Blog. When I try to add more than 5 members, it says I’m out of seats. When I try to create a team using the “Create a Team” link in the upper right of the “Manage Access” tab, it 404s. What am I doing wrong?

Thanks in advance for any help!