We've been hit with ~£30,000 of fake transactions, apparently according to our payment processor this is due to criminals using our store as a platform for testing stolen credit card numbers.
The fraud is fairly sophisticated in that they do seem to be using a wide array of IP addresses.
We have to refund these (hundreds and hundreds of transactions) as otherwise they will all inevitably end in a chargeback, which costs £15 per transaction and poses a significant risk to our reputation with the payment processors and large cost.
I've been working on this behind the scenes for a while now, and will implement some better fraud detection and add more friction to the buying process to try and stop. In the meantime, I'm afraid there's not much else I can do apart from refund them as they come in.
I really do sympathise with you that this is frustrating, but we're victims here as well and are equally as frustrated but doing everything we can to resolve this.