To change the owner of the workspace, the current owner must first change the status of the intended owner to 'co-owner'. 

Go to the “members” tab and click the “active member” status link next to the name of the person you’re designating as co-owner.  Select the co-owner field and click save.

Now this co-owner should go to the billing screen and make any edit, even something nominal like changing a 0 to 0.0.   Any person who makes changes to billing screen will automatically be converted to the space owner.

We'll be streamlining this process in a future update.  In the meantime, feel free to contact us and we'll just take care of it for you!