Walmart Self-Checkout

After shopping at the local Walmart and noticing how it didn't appear to be well stocked (except in groceries) or cleaned, I took my purchases to the self-checkout. Unlike at the grocery store, this machine did not accept my initial "Credit" selection and proceeded to try to process my card as "Debit." I pushed the button that said "Change Payment;" and it beeped and did nothing else. I finally flagged down one of the English speaking employees who pressed the exact same button. It worked for her and she condescendingly told me just to push "Change Payment." I told her that I had, but she just walked off as if she were superior to me—in that way that Walmart employees like to do.