Woolworths ripped me off !!!

I need to express my disappointment with Woolworths and how they handled my complaint, I logged an online query with them on the 1st August regarding a purchase I made on 6 packets of their houselabled Cheese & Onion Rings & ***** snacks for my kids. With the last remaining 2 packets we discovered that 1 packet was nearly empty, I weighed it on my wife's food scale and it weighed a mere 10g as apposed to the required weight of 25g, the other packet weighed 20g, it took Woolworths 5 days to respond to me and they informed me that they will conduct an inquiry with their supply and I had to give them the batch numbers etc....After not getting any feedback from them after another 5 days I logged an enquiry on there Facebook page as I gave my reference no *** only to be told that they will forward my request to the food department. A few days later I received an email of apology for my experience and a voucher to the value of R50 which I can claim at any branch. I was so furious with this response because I feel that my consumer rights has been violated and they want me to be happy with a R50, my expenses alone in claiming this voucher is way more expensive than the R50. I rep**** to the email received on the 12th August and expressed my disappointment, up until now I still haven't received any response. I am also still in possession the packets in complaint as Woolworths didn't even bother to have it uplifted for further inspection. My question is now....how many other products aren't there in a Woolworths store that doesn't conform to the prescribed weights as stipulated on the packaging ? How many other consumers haven't been ********** with under weighted products !