But they had already paid and told them to keep the money (?)

Bingo.
Plus I used to order from there at least once a month for a few years, usually more. Mostly the Two For Tuesday promotion.
It was easy, quick, and relatively cheap for what it was.

But I was telling them and proving to them that there was a problem that needed to be rectified. And the only way to do that was to show them, if I had taken anything from them then I would have just looked like a moocher.