Unfortunately this is a real problem and it can be difficult and time consuming to correct. It can be egregious in the case where an offshore company does a page-for-page copy of your site with the hope of usurping business from you, or it can be just a landing page that is copied. In either case the process to follow is the same.
There are steps you can take:
1 - Ask Google to remove the site by completing this form: http://support.google.com/bin/static.py?hl=en&ts=1114905&page=ts.cs
2- Ask the Domain Name Registrar to remove the site, in which case you must complete a DCMA TakeDown notice which you can read more about at this link: https://sarafhawkins.com/how-to-file-dmca-takedown/