Rude Cashier

Today at 07:04 I went to the Sasol Bowling Avenue to get something to eat. While I was in a queue a cashier named Kate was serving another customer who she seemed to know and was friendly with (which was not a problem). She kept on joking around until the customer told her to finish up with him so she can serve other customers. Her response to that was "haai suka" which is loosely translated to whatever and she said that while looking at the queue only to be met by me looking at her. It was only at that time that she actually stopped the joking around and asked for the next customer.

My question now to all this is: are not all customers important? Or a good services goes to those who are fami**** with the cashiers?