There a few ways to block an incoming DID using your voice gateway:
A. You can set up a reject 1-800-NXX-XXXX to stop incoming 800 numbers by adding this line under your voice grouped-trunk ...
B. You can create an ani-list and add multiple numbers to block or re-route and then add the name of this ani-list to the voice grouped-trunk area with a deny or permit. If you have any permit lists in use, of course add the deny lists above them. To do this you will have to delete the permit lists first, and then add the deny lists followed by the permits again to get everything in order.
Hope this helps!