Bad service

i bought box of fillet fish on the 18.04.2019 for Good Friday I bake it and I went to church and I have visitors when we came back the fish was like a fishcake I was very much disappointed I spend R400.00 for a rotten fish when I took it back the manager Theo told me that I must wait he didn't give credit then I phoned him he told me that is my fault I the fish out for a long time and he is waiting for someone to inspect the fish he won't give me credit I even took some example to see does it looks I always buy fish but this is the first time I encounter this kind of problem I will be happy if I can get my credit and he waste my time because I bought the fish took it back without credit and I must go back again for credit what about my pretrol time is money