No tag on swimwear

I bought swimwear for my mother in law earlier this week at the Mimosa Mall branch of Total sports. There was only 1 in the size that I was looking for, but it did not have a price tag on. Only a piece of paper with a handwritten code was stapled to the label inside the swimsuit. At the till the cashier removed the piece of paper. Today my mother in law went back to exchange the suit for a bigger number, but they are refusing to exchange it due to the fact that there is not tag on it. How am I supposed to provide a price tag that was never there in the first place? The swimsuit cost R300 and now it cannot be used due to Total Sports' bad pricing. Not impressed!!