Spammers

I may be on the wrong list here but here it goes. Can someone direct me to the right place for complaining about a US ISP who continues to host a know spammer. We can block his domain but this might not be fair to others. I have spoken to the LA providor (who I will not name as yet) after he refused to answer e-mail. However calling the US from Australia can get expensive. Any ideas where to turn?