Rudeness from a whole store manager

Worse experience at Maponya Mall from the store manager, the mistake was from their part. They had a special that was stipulated when it ends, bought the items and were not discounted and we only realised after we got home. By the time we went back there the items were no longer on special not Lunga telling us its our word against his I mean why would we make up a story... Not a apology , no responsibility taken its was just so disappointing