years ago i once actually had one call back not two minutes later. since the number didn't show i didn't put the phone to my ear lest he he try something similar, all i heard was "tough guy huh?" then he hung up before i could get him again funny thing was he never told anybody else in the boiler room about it and let the next one to call get their own ear full...
shortly after that i got the call blocking thing and now i rarely get solicitation calls