I bought a 2kg bag of chicken and got way less

I was at Pick n Pay today 22 october 2015 and i purchased a 2kg bag of PnP no name frozen chicken. I got home and was about to put it in a pot to boil when my phone rang, so i quickly opened the bag and threw the chicken in the pot not paying any attention. When i went back after my phone call to check on the chicken i noticed that there were only 4 small pieces of chicken in the bag. I wanted to take it back but my husband already threw the slip and bag away, plus i live far out of town on a farm and its a waste of petrol driving all the way to town, and that was all i had in the house for supper so we had to eat it. Even tho i dont have the slip, i swiped my smart shopper card and i can get a detailed receipt from the smart shopper app of all the items i purchased including the chicken. I really dont find this fair. I dont see how 4 small pieces of chicken cn weigh 2kg. I want a refund and another bag. Or atleast a voucher from PnP. This is unacceptable!