I wonder how this is supposed to work with workplace apps such as Slack, especially with regards to GDPR.

Say I am leaving my job, and want my personal information to be purged from this 3rd party service (Slack). They say [1] "Primary Owners of a workspace or org must contact Slack to request deletion of a deactivated member's profile information.". What if I contact the "Primary Owner" before leaving my job and they ignore my request, or better yet I have already left my job and I don't know how to contact them or who they are? Why can't I request my personal information to be deleted from a completely 3rd party American company's database myself?

[1] https://slack.com/help/articles/360000360443-Delete-profile-...