No complete refund on rotten chicken

I bought a tray of chicken and when I got home to cook it was green. When I made another trip to return it I was told to pay in the difference of the chicken I was asked to switch with at the store! When I asked about the inconvenience of bringing back the product that I had trusted to be safe to use initially I was told to complain at head office. I'm a loyal customer and was greatly disappointed at how the situation was handled and I now question the quality of items I buy from woolies.