Rude and bad-mannered behavior

I was at the N1 City Woolworths store to return items, Carmen assisted me at the customer service counter, with a very hostile attitude. I asked her if she does not greet customers, she pointed at her throat, I guessed she has a speech disability until she conversed with the supervisor. I then later realized that I did not receive my original receipt back as it had a number of items still. I went back and she saw me approaching her till, she then calls for the next customer but I forced my way to her till. I requested my original receipt, she looked for it but could not find it, I then told her to ask the supervisor that was assisting. I asked her why is she rude towards customers, she then responded that she is sick and I then asked her ,why are you at work if you are sick! She then said she got sick while on duty, I indicated that is no excuse you can still go home and be sick at home than the rude service we are receiving from you. The supervisor on duty was kind. I then proceeded to the Food Market the supervisor that was assisting at the customer service counter came running to me, to say the customers who were standing behind me notified her about the bad service I received from Carmen and she apologized and indicated that I must never leave a store dissatisfied with the service received. She then called Vivienne the store manager, who also apologized about the bad customer service and promised that she will take it up with Carmen.