My Xbox account has been Hacked. I've lost almost $800 to this Hacker. Please help.

This past December I realized that my Microsoft account had been hacked. I sent in a request for the account to be retrieved and the response I was given was saddening. They stated, that because my account had an email address with "@att.net", I was to contact
my ISP to retrieve this account.

To be clear, I do not even have AT&T as an ISP. This was an account I created a while back just to have an email. This was the email I then used to create my Xbox account. So this statement that I should contact my ISP is not true. It is a
Microsoft account, therefore I believe it is in the hands of Microsoft to help me retrieve my account. I resided to take further action since I did not see it necessary at the time. I did not believe that the hacker would have access to my payment
information. Unfortunately, that was not the case. The hacker has since then purchased multiple things without my knowledge, and I have lost almost $800 to them.

As of now, the account information has all been changed, so I have no way of resetting my password through email, or even with the Gamertag. The account, at the time I had access to it, was attached to this email and Gamertag:

Email: *** Die E-Mail-Adresse wurde aus Datenschutzgründen entfernt. ***

Gamertag: SlayzorG

The only information I have for the account right now is the Gamertag through friends. It is listed below:

Hacker's Gamertag: Salboh 2

I would like to freeze this account for further use, and hopefully get my money back. But honestly, at the very least, I would think that freezing the account would be a viable solution at this time. Hopefully, I can get a response from a real human being.
I tried all the support numbers and, every time, I was directed to a robot. This would have been much easier to explain if I had been able to talk to a human being. I understand that with high volume robots are better, but at least have an option to try and
reach a human. Anyways, I hope this reaches someone and I get a response.

Thank you.

:)