As an Admin on the environment that had similar issues. I create a DocuSign case to close free or personal DocuSign Accounts that have the same email address for each of the accounts. There is a Account Admin "Users" feature where you can search the email address to see all Accounts associated to that email. I then grab the Account number of the Account I want closed, create a case to outline the closure clearly then make sure to add the User email address so they can be contacted directly to approve closure. Typically turn around is 24 to 72 hours to get the account closed if the User responds quickly to the closure request.

This issue really only is found with Users who were able to create Accounts prior to the SSO implementation as your "Claimed Domains" should stop future accounts from being opened.

If you are an Organization Admin (you must have an Org account to be one), you can use the bulk actions "Close Users", "Close external domain users" feature with a CSV file containing the user information to close all external domain users :

AccountID, AccountName, APIUserName, FullName, FirstName, LastName, UserEmail

These users created accounts even though we had SSO account.  How can I see the account # for the free trial?

For Freemium accounts for “claimed domains” that have been closed. 

Is there a way to delete all data immediately? Or do we have to wait 2 years for documents to be purged/deleted. See URL below:

“When an account is closed, Docusign purges all sent, signed, and voided envelopes that are older than two years from the account closure date. User information is also purged from the account“

Source: https://support.docusign.com/s/document-item?language=en_US&rsc_301&bundleId=pik1583277475390&topicId=frq1583277404325.html&_LANG=enus