Not sure if trolling...or just that stupid...

So one of the jobs I work at is a mini-mart/gas station (a great hub for stupidity), and I had one of the best stupid customer fails last week. Note: All our pumps are pre-pay inside or credit only. This is important.

Guy came in wanting to pay for his gas using a discount program we have...I think the conversation that follows speaks for itself:

Customer: "So I used my points card at the pump and it told me to prepay?"

Me: "Sure, if you're paying cash, I can just run everything in here. Just cancel the transaction out there, come back in, and I can take care of the rest."

*Customer leaves and comes back in a minute later* "How do I cancel the transaction?" (Note: The pumps have a button on them clearly labeled cancel)

*After canceling the transaction for him* "Okay sir, now, if you come back inside, I can run the transaction."

Customer: "Okay." *hands me his card* "So if you run this card inside, I can pump, then pay you, right?"

Me: "No sir, you pay inside, then pump."

Customer: "Oh, so if I run my rewards card out here, then pay you inside, I can get my discount?"

Me: -_- "Sir, you just tried that and it didn't work. I run both the card and the payment inside, then you pump."

Customer: "Ohhhh...but how do I know I got my discount then?"

Me: "...It shows it at the pump sir."

Customer: "Oh okay." * Proceeds to slide discount card at the pump*

The worst part is, I had the exact same thing happen not five minutes later...with a different customer...-_-