Account Hijacked

I'm sorry to hear about your problem. If you still have access to your account and it has been compromised, please follow the instructions at this link: https://support.microsoft.com/account-billing/how-to-recover-a-hacked-or-compromised-microsoft-account-24ca907d-bcdf-a44b-4656-47f0cd89c245

If your email address was changed by the hacker, you should use the ACSR account recovery form.

You can also use this form https://aka.ms/recovermyaccount, which will be sent to a team specializing in this type of problem. (Although it mentions Xbox, the form is also for Microsoft account recovery.)

Use this guide to help you fill it out: https://support.microsoft.com/account-billing/guidance-notes-for-the-microsoft-account-recovery-form-4dd8fef1-33d2-4fbe-9352-66127ab9b50e

You should receive a response by email. It may take up to 72 hours.
If you do not receive a response after this period, check your spam folder.