PERMANENTLY delete customers

[peggy king]

Due to being spammed with registrations by robot, I have some 900 spam registrations/accounts that I have PERMANENTLY deleted in Presta-shop.  They no longer show when I look at my customer list, but they're still there as evidenced by the number of accounts PS shows on my dashboard.  Worse, they go over to Mailchimp.  I have deleted them from MC too.  But I had to do a re-connect between PS and MC, and they came back into MC, so I had to delete them again.   How does one PERMANENTLY delete those spam accounts from PS?  I don't do html, using PS 1.6.18