It would be nice to be able to block a specific phone number because sometimes I get phone calls from telemarketers, and sometimes other spam, not to mention people from our past we don't want to hear from anymore.
Unfortunately it isn't that simple. Koodo can't block a # from calling you on their end.
However, you have 2 options:
1. I don't know what phone you have, but search your OS's market (App Store, Google Play, BB World, Windows Marketplace, etc.) for a number blocker. You might still get notifications about the phone # that tried to reach you but at least you can have it rejected.
2. Change your phone #. That way the undesirable callers won't be able to reach you anymore.