Report facebook about the problem.They shoud have a policy to deny/block the person.

If you are talking about email then unsubscribe or email to abuse@domain.com by just google whois with the domain name and you should get technical contact information.

Here is the link:
http://www.networksolutions.com/whois/index.jsp

If it doesn;t help then ping domain.com and  get the ip address and
search for the abuse email contact  ip information or ASN at below link:

http://tools.whois.net/whoisbyip/

Regards