Found a DG store near me, with a clerk willing to try the load. However, he didn't think it was possible with the store's registers. Indeed we both looked at his menu, and none of the 9 items looked like the prepaid loads. We tried 2 options unsuccessfully, then decided to abort when another customer came to the checkout.

Has anyone succeeded in loading Serve at a DG? If so, what would be the right buttons to press for my checkout clerk?
TIA