Multi accounting.

How do you report players for using multiple accounts?

email to [email protected]

And wait. The report states it may take up to 72 hours for a review and/or reply to your complaint. That is in the BEST case scenerios. More times than not, it is reviewed after the damage has already been done and your game lays a smouldering pile of ashes. Best of luck to you in you endevors though.
And if any disagree with that assessment, prove me wrong. There is a line forming that says otherwise.

Still, even if it doesn't benefit you, better to report.