Someone has put my phone number on their email account

Someone has hacked my account and put my phone number on their own email. When I try to log in the security info, for verification, is going to the other persons email account. I have changed passwords, usernames and everything I can however I cannot get my phone number removed from going to this persons email and not my own. I cannot use the sign in helper as the email is not on my account but they have taken my phone number. I now have an xbox account linked with my phone number(I do not have an xbox), this is all coming under the umbrella of my Microsoft account.