Not good news I'm afraid. I've spent a year trying to figure this out, and have learned you can block a few individual numbers, but the marketers use dozens (hundreds) of numbers, calling through computer calling systems.
You can't block them all.
Usually, you can block up to a dozen or so, but as they change their number, good luck in blocking them all.
If all your calls are definitely from the same number, you can block it. But how do you know the number that shows on the Caller ID is actually the number they're calling from? And if you block that one number, they'll probably just use another from their "pool".
Oh the stories I could tell ...
One technique: completely turn off the ringer, and let callers leave a message. Then call them back if you want. Nine times out of ten, marketers don't leave a message.
Tom