Offers no refunds

They are refusing to refund me for a stroller I bought from them, I have not opened the unit its still sealed on in the original packaging and I returned it within 20 days after my purchase with my slip and warranty sticker. They are refusing to give me a refund and claim that in good faith will only offer me a store voucher and I should be glad they're not sending me home with the product I don't want(Yes this is the exact words from them)! They were rude and unhelpful when I phoned the Durban head office, I spoke to a lady Roshni.