Hey there! Nice to meet you!
Kindly secure your account by enabling the two-step verification feature and ensure that your verification methods are updated on account.microsoft.com > Security > Manage how I sign in
Also, please make sure that there are no unfamiliar email addresses/phone numbers added to your account's security info on account.microsoft.com > Security > Manage How you Sign in.
Note: Ensure your account's security info is always up to date and that you have access to it.
If there is an unfamiliar email/phone number in your security info, click on Manage, then remove it.
Then please follow the guide from this thread to prevent unauthorized logins: https://learn.microsoft.com/answers/questions/4049625/someone-is-repeatedly-trying-to-access-or-hack-my?forum=windows-all&referrer=answers
You may also check this link for more information on how to secure your account: https://support.microsoft.com/account-billing/how-to-help-keep-your-microsoft-account-secure-628538c2-7006-33bb-5ef4-c917657362b9
Thank you for your understanding! Please feel free to let me know if you need anything else.
Best regards,
Darhyl