Block some Destination to Provider
From Kolmisoft Wiki
Block Destination to Provider
In case, if Provider does not allow route via particular Destinations, you might need to block it on your system as well. You are able to block a special prefix (Destination) by setting "-1" or "Blocked" Price for chosen Destination in Provider Tariff.
There is two ways to set Blocked Destinations. You can set it by importing Rates from CSV with "-1" or word "Blocked" instead of price or changing Rate Details manually