Can customers change their own billing data via pulumi.com or do we have to reach out to support?

If you’re paying with a credit card, you can change that, and you can change some of the properties of your subscription, but you can’t (yet) change your billing email address; you’ll need to message support for that. (It’s on our list of todos for this month to get that added, but as of today, it’s still a manual thing.)

Specifically, org admins are able to update credit card info.