"Sir, your card is being rejected. Do you have a VISA card that I can try? It seems for the past few days, those are the only ones that seem to work for anyone around here."
This would be a bit of scumbaggery but pure marketing genius I say.
Is there any technical barrier that prevents the swiping machine from accepting another card? If so, you could literally show them that "Look, it isn't working"
This would be a bit of scumbaggery but pure marketing genius I say.