I do the same, but my contact is labeled $PAM (Spam) with a photo of Spam and assigned no ringtone. On Android, I can also mark the entire contact as "Auto Reject".
"Pamela" this caller and one yesterday from another number ask for "Pamela." When I tell them they have the wrong number; they suggest that I can help them....that they are calling from "Courtesy Call" on behalf of a foundation.....