Refusal to exchange faulty item

My sisters bought two shirts for my husband, and when I washed one of them at the recommended temperature it shrank considerably. My husband tried to return the item in Port Elizabeth, but they said they would not exchange it or give us the full value of the shirt that my sisters paid. Instead they insisted that they would only give us the lowest sale price of the item - less than half of what my sisters paid. My husband would have had to swap both shirts and pay extra to get one in exchange. This seems inexcusable to me as it was the product which was problematic. My experience of Woolworths has always been that they are amenable and customer focused, so we were surprised at what seems a very unfair practice in being unwilling to exchange a faulty product. We would really appreciate it if you could look into this.