Caller: someone with a Netherlands phone number

Lady called saying she was from Amazon, and I'd been charged $39.90.. I've had calls like this before, where they try to tell you someone else has used your credit card, and want to check our details etc.. I said I haven't been charged anything... she tried to tell me I had, and I said how? which card? I'm sure you don't even have my card, then she hung up, knowing I was wise to her scam. How do these scammers sleep at night!