Sorry to hear that you’re having trouble with this situation. Changing the password may not always immediately disconnect every active session, especially if the account is still connected to other devices or services.
Please sign in at the following link and use the option to sign out everywhere: https://account.live.com/proofs/manage/additional
Please note that this process may take up to 24 hours to fully sign out all active sessions. After that, I also recommend reviewing your recent account activity and removing any devices or sign-ins that you do not recognize.