Poor customer service

I have never been so angry and disappointed with a senior staff member from truworths Mall@Carnival branch her name is Gloria. She was so rude and left my sister unattended. My sister went to go exchange a dress my mother bought with her account she had the slip. Gloria the manager told her that exchange can not happen without account holder ID and clinic card. I was extremely shocked as to why a clinic card would be a requirement. I sent a massage via truworths WhatsApp and response I received from them was really concerning, they stated that they can confirm that a clinic card was not requested. How did they confirm that ? With whom did they confirm that ? When both my sister and mother were never called and asked. So in other words Truworths took their staff word and called us liers ? Truly disappointed at how this case was handled. Poor customer service from a senior manager is unacceptable.