Because you may have a (commercial) relationship with Atlassian, you cannot just delete your account, of course. Instead, contact them using the link named. Of course, use the email address linked to your Atlassian account.
URLS:
http://www.atlassian.com/
http://www.atlassian.com/company/contact
Please note that AccountKiller.com is not associated with the business listed on this page. AccountKiller provides easy-to-understand instructions and guides on how to cancel charges and relationships from the list of businesses on our site, we have no affiliation with these businesses.