Hello thanks for posting on the Community!
While one-time static data uploads for Org Charts are available on your subscription level; data refresh replace and overlay are Enterprise-only features. I would recommend creating a new Org Chart and re-importing your updated dataset. Otherwise if you are looking to upgrade in order to have access to those features please visit our pricing page. Hope this helps!
For anyone else that has questions about the intended functionality of Org Charts please check out our Create an org chart. For details as to the functionality and features available at each subscription level please check out our Account Types article.