Bad service from Pick n Pay Waterstone Somerset west

Pick n pay Waterstone in Somerset West W/C refused to give us an that was clearly discounted and not showing on there tills; saying it is not discounted although it was advertised marked down in store with a big sign. casher called supervisor to check but the supervisor had no customer service skills and also told me that I can't get item that was clearly marked by a big sign! After I told my side of what I thought of the service received as a customer I was basically told whatever and that they don't care. Super disappointed in the service and still very unhappy. I would like a call from the store manager.