Hi and welcome to our Elastix forum. :wink:
At first, if you believe that your server is hacked, try to improve the security. (There's several thread and documents on this forum and on this website).
Next if you want filter some directions, you could setting up a code PIN. When a route will be selected, a secret code will be asked before the dialing number.
It could be true for any critical numbers (Mobile calls, international calls ..etc)