Pretty convincing the number's not one to answer at all if you can if you look at the prefix. If you're answering at all, that's a great way to get more calls. Times a live voice answers may be noted and relayed to other pests so they'll know what time is good to call. Thwart all by letting the phone ring.
They have called me 30+ times over the last 3 days, they have even called me private. Talking about a grant. I have asked them not to call anymore, but they keep calling.