Lay-by policy not explained

I did a lay-by 3 months ago worth R3000 when I got it and went home with it the items were small….and there were mice **** (faeces) all over the bag …I should think that I might have a mice in my house or it got out of my car while driving back …I’m very scared of rats…when to the store to get a refund but was told I can only get a gift voucher which was stated to me when I did the lay-by or when I fetched it …. I would like my refund I’m not interested in buying anything from your stores worth R3000