For security reason, you cannot change the login email under account settings. However, it's possible to remove the old email address from your OCP account and meanwhile add the new email to your OCP account.
3. Log in with the old email address and make the new email administrator of your OCP account.
4. Log in with the new email address and remove the old email from your OCP account.
Read more: How to remove a user from my organization?
Now you can to log in to your OCP account with the new email & the old log in email is deactivated.