Zara.Mall of Africa manager in men's department

My son bought a trouser at zara mall of Africa upon arrival ING at home he discovered there is no button on the trouser but because he was traveling overseas he asked me to return it for him,when I went there during the week I found a very friendly lady who referred to another guy to check if they have the same trouser and he checked using a barcode to check and he said there is no stock available and wrote my name on the book ,promise to call me as soon as stock arrived, boy when I went to enquire I was met by a rude tall Indian guy and rude floor manager a black always wearing boots, and they were insuating that I was lying since I dint take the name of the guy who was helping ,finally they aggred to take the trouser to the trailer,when I went to fetch the trouser today the lady manager was still rude,she did not even bother to put the trouser in a plastic bag I had to take just like that my question is why is big shop like zara still hire rude managers like that ,I am not very Happy