To block the broker you need to find "customers" in "Customer management" Section

Then use table filter to find broker that you are looking for

Then type broker name that you want to block

Open Broker profile by clicking to broker's name

Change status to "Blocked" then click to "save" button in order to save changes

Then go back to "Load Management" section to check broker's status click "+ New Load"

to create a load then look for broker that you blocked once you select blocked broker you see this notice