Just had a weird spam call: A bloke claiming to be "Peter" from Safecom or Safe.com just called, he said that he was just calling to let me know that they'd taken payment of £79 from my bank card as payment for their service which prevents unwanted phone calls (ironic eh?

). I said you'd better not have taken any such payment at which point he started saying that his colleague had called me 4-6 weeks ago and that I'd agreed to this service. Now there's no way I'd pay for a service like that, I'm just too tight! Nor would I have given someone who'd cold called me a credit card number over the phone, so I knew he was talking bollocks! Having explained this to him he got a little shirty and said that I'd made a mistake and that he could assure me that they had taken the payment, and I should check with my bank. I said I would and ended the conversation.
The thing is, I don't understand how such a scam would work. They aren't asking for money (cos they claim they've already taken it), so what's in it for them?