Hey there! Nice to meet you!
I'm sorry you are experiencing this.
Since the security info has been replaced by the hacker, I'm afraid there is no other working method to recover the Microsoft account, and Microsoft Support cannot help either.
However, I would recommend reaching out to Microsoft Support regarding your open case, and they can possibly "Suspend" the account permanently once they have confirmed that the account can no longer be recovered in order to prevent the hacker from using it:
Type "Microsoft 365 sign-in problem" > Click "Get Help" > Scroll down and select the option "Sign in to contact Support" > Microsoft 365 and Office > Billing and Account Profile Questions > Confirm > then select "Chat with a support agent in your web browser"
Lastly, you will need to reach out to your bank/financial institution immediately to dispute the fraudulent charges and request to block all charges from Microsoft to prevent further unauthorized purchases.
You may also need to request a new payment method.
Thank you for your understanding.
Best regards,
Darhyl