Over billed at Shoprite with no reason or even promise to pay back

Shoprite u save is cheap because they say they save money but is it true? I was at Shoprite usave Klipgat and swiped my card the lady said it declined n she will swipe again now when I check my balance she double billed new and she said it wouldn't and now I call them there's no response, if I ta take a taxi or even drive there to go ask for my money back who will return my transport money?