I keep receiving faxes from this company and there is no answer at the number they give for unlisting my number.

Here's some information about www.number-privacy.eu. The domain was registered on April 26, 2011 by:

  Alan Morgan
  Datext Ltd.
  Crows End
  BA13 3EB Westbury
  Wiltshire
  United Kingdom
  Phone 044.1373300046
  Fax 044.8707626245
  Email datext@blueyonder.co.uk

With the domain number-privacy.eu these spammers are trying to make it appear as though there is actually some way to get removed from their spam fax lists. In reality, whenever you "opt out" you're just confirming that you received the fax and actually read it, so you'll be added to even more fax spam lists.

Spam fax received regarding vacation packages. The number 1-800-976-3053 was shown as the number to call to be scammed, err, I mean, to sign up for a vacation. As always, these parasites don't show their company name on the fax, and they don't send any CLSID information on the fax header. They also claim we can be removed from their list by calling 1-855-467-0212 or at www.number-privacy.eu.

Vacation Memo, received by fax

Same here.

sending cheap trip requests at our business number