The 3 ways to Disable/Delete a configured credential that is active for a user are:
1. Use the ca-strongauth-sample-application
to Delete/Disable the credential in question.
2. Use the Webservice calls DeleteCredential and DisableCredential to Delete and Disable credentials (in that order).
3. Use the Admin UI's (Global Admin UI) "Manage Credentials" screen to Delete or Disable the credentials for the given User.