Bad service and attitude given by your till controller or till manager

So Saturday went to mrp in mamelodi to exchange shoes that I had purchased online and I was so disgusted at the service and attitude i got from your manager or till controller Martha. I have worked in customer service for more then 6 years so the same service I give I expect that from other institutions. She has attitude even her face is not friendly or welcoming at all. She has a angry Face like its our fault that we said she must work where she is working. She didn't even have the decency to tell us as customers that they tills were jammed and needed to be rebooted and the queue was long. I have experienced her unpleasant attitude more then twice as I purchase online and fetch my parcel there at the mamelodi shop. I must say you guys are loosing me as a customer due to the poor service I got. Do something or I'm gone for good. Even now when I look at th3 mrp shop be it anywhere I feel kinda disgusted and the thought of the service I will get there.