And even if it was a cold call, the extra step of pressing *5 only assures that a human is on the line who won't be stymied by it. The service being provided is pretty gimmicky and relies on honest humans, a quality you won't often find in telephonic sales.
You'd think so, wouldn't you? But my experience using a phone at home that has BT Call Guardian built in (does very much the same job as the device in the Amazon reviews), is that it stops 100% of nuisance calls. It seems the spammers either can't, or can't be bothered to, go through the call screening steps.