How to change phone number from the Microsoft account? - Microsoft Community

someone knows email , he/she has changed password of account need change number of account

how microsoft account if it's been compromised

https://support.microsoft.com/en-us/help/10494/microsoft-account-get-back-compromised-account

you can check recent activity on account

https://support.microsoft.com/en-us/help/13782/microsoft-account-what-is-the-recent-activity-page

Mobile Devices / Other Windows mobile devices