Selling underweight products

I recently bought 3 bags of nestle mini chocolates from woolworths and all 3 bags were short of between 1 to 3 chocolates per bag which were all under the weight stated on the packet with one packet being 20% underweight. I logged a customer complaint and the nestle company stated that it was within their right to do this. I was not happy with the feedback and called woolworths customer care and the lady said there was nothing they could do as it wasn't their product. I do understand but no attempt was even made to find out to what extent the products were underweight. Its sad that we are charged full price for products not up to spec. Disappointed with woollies.