Insulting Customer

Me and my fiancé went to MTN in I'langa Mall to apply for a new contract. After she was approved, we asked the consulted, Lucky, to please phone another branch to see if they have stock. In the conversation between Lucky and the person on the phone, Lucky referred to my fiancé as the fat white woman. Unfortunately for him, both me and my fiancé understand his language. We asked the other consultant if we can speak to the manager, but was refused. Since when is insulting customers good for business? I will NOT visit any MTN store or consider any MTN promotion until that person is punished accordingly, and neither will my friends or family, which I have already notified about what happened. My brother is already on his way to town to get a Telkom sim card and wil not be using MTN anymore.