non rufinding of money on unopened goods

I bought dream tubes for my 22 month old twins beds.after assembling the beds we saw that it doesn't fit into their room so we decided that we rather buy two toddler beds. These beds are R1400 each. We decided to return the dream tubes seeing that we didn't open and even take it out of the baby city bag. When returning the goods they refused to give me back my money (R800). I explained that I dont need a voucher seeing that they don't sell the wooden beds that I need and that I need my money in oder to pay for the beds. There is nothing in the shop that I need now I need to by my babies beds. I didn't even have the goods with me for longer than 24 hours. I don't have money to throw away seeing that raising twins is expensive. I want my money back.