Refusing exchange

We paid nearly R400 for a dress. Unfortunatly it was the wrong size now they refuse to exchange it. Giving the dodgiest excuses. We did not ask for a single cent back we only want a different size. The area manager refused to speak to us 4 times the manger phoned her and when she eventuallu does she screams and shouts at my husband. Telling him there is absolutely nothing he can do. I have never in my life seen worse service. I truly hope that everyone think twice before buying anything from them