Pineware 2 plate stove

My mom went and bought a Pineware stove 3 months ago. One plate is not working and the stove has a 1 year warranty. I sent my sister with the receipt to return and get another one, the store manager who hid his name with his red waistcoat and cashier mocked my sister and said the stove looks like its 3 years old and assumed that we got the receipt from someone else and they refused to assist us. This is one of the new model Pineware 2 plate stove and the quality is not good because it rusts but they refused to listen to any reason and said they will not assist us even when another client was testifying to how quickly the stove gets rusty but they refused to listen and mocked my sister. Pick n Pay Chatsworth has the worst service ever