A sure tactic to prevent repeated phishing or telemarketing calls is to simply scream obscenities at the very first call. Non-stop. Insult the caller’s mother and ancestry. Do not let the caller get a word in. The caller is not allowed to be the first to hang up except under verifiable abuse, so your maniacal (is that a word?) screaming will get recorded. The head honchos will then hear your recorded tirade and in their infinite wisdom will decide that yes, maybe this phone number really does need to be eliminated from the automated dialers since the screamer is very obviously not a sucker.