Someone hacked my email account and changed the alternate email and phone number

Today I tried to access my other hotmail account (*** Email address is removed for privacy ***) and couldn't because "It appears that someone else might be using your account". I tried filling our the verification form but the information provided was deemed insufficient to establish ownership of the account. I tried resetting the password but the phone number and alternate email address are not mine, so I will never receive the code. I've also chatted with a Microsoft agent who after failing to provide me with a solution suggested I post my problem here.

I'll be happy to provide further information to establish my ownership of the account, but please help me!

Thank you,

Agustina