[Exim] deny domains how?

I am trying to figure out how to deny any email from
the whole SBC network as that company is out of control
with spam and I am tired of adding all of the SBC
IP blocks to my local_host_blacklist file.

This is in my 30_exim4-config_check_rcpt file:

deny domains = *.ameritech.net
deny domains = *.swbell.net
deny domains = *.pacbell.net
deny domains = *.sbcglobal.net

But it does not work. How do you make Exim deny based
upon a reverse DNS lookup?

I want to reject anything that looks like this:

Received: from adsl-69-208-77-71.dsl.klmzmi.ameritech.net
or
Received: from adsl-66-141-144-84.dsl.hstntx.swbell.net
or
Received: from adsl-68-126-249-36.dsl.irvnca.pacbell.net
etc...


Thanks,
Andy