You block them individually, after call comes in. You do it in your cell phone, as if you're going to add them to your contacts, but scroll all the way down til you see "block this caller"
There are numerous threads here dedicated to discussion of call blockers. Additionally, you can search for call blockers, choose the one you want, and purchase at the place of your choosing. Any other discussion in the number threads is not allowed.
You block them individually, after call comes in. You do it in your cell phone, as if you're going to add them to your contacts, but scroll all the way down til you see "block this caller"