When ISP doesn't hear a spam report

What to do next?

[silverbytes]

What steps do you take when an ISP is allowing a user to host a website for sending bulk unsolicited emails?
The user is hosting the page to offer email databases, bulk sending and stuff like that.
Besides he's using isp relay.
Reports to abuse at isp doesn't have response and page is still there.
How do you go for someone above them to stop it?

[moishe]

Why not report the IP blocks of the ISP to sites like [mail-abuse.com,...] [spam.org...] and the like. When suddenly all of their customers start seeing their email bouncing back, it might get their attention.

[silverbytes]

That's a good idea. Unfortunatelly those sites are so uncomprehensive to most of users that you get lost before you can nominate the spammer.