Hi Drew! You are correct that you have the ability to block specific numbers from calling your client, but there are a couple of other things you could implement that may be helpful in this instance:
When you set up a keyword tracking pool, there is an automatic spam prevention tool built in. This lets CallRail determine if the keyword tracking numbers in your pool have been assigned to visitors on the site. If a call comes through and your numbers haven’t yet been assigned, CallRail challenges it with a message that says “your number hasn’t been activated yet.” This message challenges calls to keyword tracking numbers that have not been recently assigned. You can check to ensure this default setting has not been turned off by following these steps.
Aside from blocking numbers one by one as they call, you can choose to filter callers by category and then block or call any number that falls into that category.
You can find detailed instructions for doing this here.
Let me know if this helps!