How should I proceed to claim/dispute a Facebook Page?

I am part of this group that is promoting a popular movement.

In advance of us hitting the streets, this anonymous person registered the page and started getting followers.

It’s published as the official page of the movement, yet the communications group has no access to it.

More, the page is not updated. Only fans post stuff there. Nothing official is being published, which is making us lose steam.

How can we go about claiming/disputing the page? Any tips?

It would be cool if we could go about this another way, but the administrator doesn’t reply to any of our posts requesting contact.

Thanks for your insight/experience.