Why can microsoft not recover my account?

I got an email from CDOC case managment that pretty much said: We have enough information from you that we know you owned the account originally, but we can't do anything because the hacker has changed the security details. Like what? The whole point is that the hacker has changed the security details, so I can't get in. All I want is my xbox account back, and some people are saying that they can transfer it, but I don't know. The hacked account has been suspended and I've asked them if they can just transfer the xbox account, but I don't know.