The Walmart-backed financial technology company, One, is helping customers to buy now and pay later.  The payment option is being used in some of Walmart's stores. The Arkansas-based retailer has over 4,000 stores around the U.S. but it didn't specify which stores are using One. One declined to comment.  AMERICANS USING BUY NOW, PAY LATER TO AFFORD GROCERIES, OTHER NECESSITIESAccording to One’s website, the pay over time feature applies to purchases between $100 and$3,000. It also comes with an annual perc ...