Hey miyabik,
Sorry to hear someone else had gotten into your account. If you haven't already, please be sure to go through as many of these security steps as possible to help get your account and system back into your control.
After that you'll need to get back in touch with our support team to help recover the account itself. As they'll need to discuss private account details, that is not something we can assist with here on the forums. I do see you've already reached out, but if the issue still was not resolved, you'll need to resume a previous case or create a new case so another advisor can take a look.
They do need to be able to verify a certain level of information to make any changes. I can definitely understand that's harder if the original email is old and no longer accessible, but you'd need to continue working with the advisors to see what other options may be available in this case.