Managing personal Outlook.com account settings, security, and privacy
@Stream said
it said my username (meaning email) didn't exist. ... when I tried to create an account, it said it already was
Microsoft never reuses an email address. Even if it has been deleted and/or the account has been closed.
and I soon realized that someone had taken over my account ... but how did this person manage to change my password, email, and subsequently my number?
Once the hacker has access to your Microsoft account, they can change your account ID and all of your Security Settings
I just wanted the opportunity to talk to support about the situation, but I can't even do that
Microsoft Account Security is an automated process. Microsoft Support Agents can not unlock an account, reset your password, or change any Security Settings no matter what documentation you can present. They won't be able to tell you anything beyond what you already know - Your account was hacked.
Microsoft has made the automated recovery process untouchable. No human can exert any influence on your behalf. No human will ever look at your Account Recovery form. The automated process checks only if you have answered the specific questions on the form. Anything else is ignored. It is normal to get an immediate rejection.
I am sorry. I know that losing access to your account is more than just an inconvenience, it can cause real hardships. I wish I could give you another answer.