The ATLAS was not designed to do any call routing/blocking based on the ANI.
There is not a "good way" to block specific ANI, but if the NETWORK TERM is a PRI, there is an option under the IFCE CONFIG for the PRI to "Swap ANI/DNIS". If this is set to ENABLED, the ANI and DNIS are literally swapped and the call is then routed based on what "was" the ANI prior to the swap. You can "block" the specific ANI by accepting that ANI to a "dummy" interface (like a module that is not actually installed in the ATLAS). Since you cannot specify the ANI you WANT to accept, the only way to block the specific ANI is to send it to a dummy interface.
There is a problem with this method, though, and that is if no ANI is presented. Once the ANI and DNIS are swapped, there is nothing to route the call on, so it will not get routed. Also, depending on your end equipment and the connection to the ATLAS, you may need to swap the ANI/DNIS back to their original values. If you have a PRI in the USER TERM, you can simply do another "Swap ANI/DNIS". If you do not have a PRI connection to the end equipment, but need the DNIS and/or ANI presented then I don't recommend setting this up.
Hope this helps,