A Microsoft file hosting and synchronization service.
I wish I had better news for you, this forum is just a user to user forum, for security purposes, no-one here has any account access, when a Microsoft account is hacked, if the hackers change the associated data like the Email or if 2 step verification is enabled on the account, then that account is usually no longer recoverable, try using the process they provide on this link to recover a hacked account, if this process is not successful, sadly, that account cannot be recovered.
If your account is not recoverable using that process, if you have a subscription to Microsoft 365 linked to that account, you will need to contact Microsoft Support directly to cancel the subscription on that account, try using this method to contact their support.
Go to this link: https://support.microsoft.com/contactus
Select Microsoft 365
Click 'Get Home Support'.
In the box provided, type billing.
Press Enter, then on the next page, scroll down and click 'Sign in to Contact Support'.
Navigate to Microsoft 365 and Office - Manage my Subscription.
Select the 'Chat with support agent in web browser' option