UberEats failed to pay my refund

The code given was not app**** and it did not inform me, I only saw after the order was placed and within seconds I canceled the order, it was not my fault that the promo code which I was given by uber eats was not working. when I requested for my refund I was told that I can’t be refunded because they’ve already started preparing your order. Now I'm left with no food and R200 was taken from my account