Expired meat

On Monday the 28 March my husband and myself bought meat at Checkers (Pork Texan Steak) at Checkers Hyper Northcliff corner. At the time the meat was done braai we removed the plastic and we realised that there was a funny smell but at the time we thought it was the meranade, and as we were eating the meat had a terrible sour taste.. I am really not very happy, as we all know wrotten pork is very poisonous, as a very concerned customer what if we ate the meat and something happened as i have two small boys ages 6 and 7 what if we did not come across the smell and taste and they children ate it? How could they have sold such meat, as the sell by date is the 31.03.2016 and I am not sure how long before the sell by date should goods be removed from the shelves. I have the receipt, I also took pictures of the meat and the barcodes on the package, which I would like and email address sent to me so that I can foward the pictures I took.. My receipt number ***..