It’s exist actually, however, right now it’s a manual process, which requires to file a support request.
We would process it and your account would be deleted if you do not want to use a Storj network anymore.
We are working on of the self-service, but it’s not released yet (you can try it on the QA Satellite though: Please join our public test network).
However if your account is frozen already, you can do nothing - it would be deleted automatically (but no ETA and no notification would be sent).