If an attacker changed the username, password, MFA number and recovery code of a Microsoft account - which any smart attacker will do within minutes of gaining control of an account - there isn't anything that you or Microsoft can do to fix it, which is why there is no one you can talk to. There's nothing to say: the account is no longer yours.
What you need to be concerned about now: The attacker knows everything about you that's in the account. If there's enough usable information in the account, the attacker can impersonate you on the Internet.