Ordered a Large R47.90 Krusher but Received R33.90 Krusher

I ordered a R47.90 Oreo Krusher on the KFC app and they delivered a Small Krusher that has the price of R33.90. Then take so long to get through customer care to be through the store to rectify their mistake. They only offer you a vochure or refund.. What are we to do with that when we ordered a product that can't enjoy. Their refund takes 7 working days