We have all probably experienced this one at least once: phone rings, just once.
You return the call. Nobody answers. Or you are put on hold. You hang up. When your phone bill arrives, it's kind of high, and you shrug your shoulders.
Or it is horribly high and you don't know where this came from ...
It's all about abusing your perfectly natural reaction: when somebody calls you, you turn and say at least: "What?"
When somebody phones you and rings just once, you think it's rude, but you still return the call. Maybe the person dropped the phone, maybe he lost signal, maybe his account is empty but his message is urgent ... Your human reaction is to react. You don't immediately think that they are after your wallet.
Before you know it, you're a victim of a phone scam called Wangiri.