Spammers are hitting mobile phones more and more aggressively. (Guardian UK)
It uses computer-generated calls to ring target phones just once so that a number is left behind as a missed call. When users ring the number to find out who has been calling them, they are answered by someone saying "customer care" then the voice goes into the "congratulations" spiel. The caller is then referred to a premium rate number where they can find out more details of their "fantastic prize".