Cashier using a phone whilst assisting us

A Cashier by the name Nomvula Nkambule did not greet us (my sister and I) when we arrived at the till point , then she went on chatting to another shopper (who seemed to be her friend), then she took the Shopper's phone and added her numbers and stopped scanning our items. When I tell her what she was doing was wrong, she gave me an attitude, she further stated that what she was doing wasn't wrong then gave me my change with an attitude as well. She just placed my change on top of the counter then she assisted the next customers.