[anti-abuse-wg] What to do when "abuse" email address does not work?

I have found that many "abuse" email addresses indicated in WHOIS databases actually are fake e-addresses. One of them is gestionip@TELEFONICA.NET.PE (because my company has received many many spams originated from its network so I wrote a spam complaint to this e-address but the mail was rejected for non-existent mailbox!) What can we do in this case? Thanks