Burnt horrible Cake!

I paid R650 for my daughters birthday cake to later learn on the day when I cut it that it was burnt! I visited the store to lay a complaint I was first offered a small Cake which I do not need and declined then reimbursed with a pathetic R100, silence and horrible customer service as a cherry ontop! When I asked the lady if the R100 is all I am getting she responded by saying there's nothing more they can do about this matter! They are clearly not clued up with the treat the customer fairly policy nor the CPA as a whole I am disgusted!!!!!!!