Bad customer service with no regard for a customer when the employee was at fault

Today I had a terrible experience at Spar in Parklands. I bought 3 items today and when I walked away and checked my slip there was 4 items listed. I checked the slip because the total did not add up and then returned to show the cashier that there was an item on my slip that I did not bring to the till. I was then trying to convince the cashier that I did not buy the item she insisted I bought. I then went to look for a supervisor who told me with an attitude that she will have to call the manager. I then asked her to please do that but then she walked away and I stood waiting for a while until a man pitched up and took my slip and walked away. Nothing was said to me and ALL the cashiers were chatting in a language I didn't understand about it. At no point did anybody in the stood explain to me what was happening, why I was left waiting and what the procedure was. When the man walked away I asked him to explain to me why he was taking my slip and if he could kindly explain to me why I was standing infront of the stoor like a theif being judged by all the customers ans employees around. He then with a completely irritated and dismissive attitude told me that they will refund me because the camera showed that the previous customer bought the product. The manager DID NOT explain to me how this could have happened, never properly listed to my side of the story or kindly apologized for the fact that I not only waited in the stoor but was accused of putting the item in my bag by the cashier. In my attempt to explain to the manager that I wasn't even out of the stoor when I turned around to advise them of the error he walked away and said that it was procedure. I don't expect this sort of attitude and dismissive behavior from SPAR employees and find it really upsetting how I was continuously spoken about and not spoken to directly. I am extremely disappointed by this service and there was absolutely no regard or accountability taken for the mistake made .