Hello,
This is a third party email address, right? Meaning, not an outlook.com or hotmail.com address, right?
If so, contacting Microsoft actually won't go anywhere, because Microsoft cannot verify ownership of a third party email address, hence there's no way Microsoft support can help make an existing Microsoft account go away based on what you tell them.
However, go here instead: https://msrc.microsoft.com/report/
Scroll down to Outlook Spam section and report it there, as you can likely report it as an impersonation.