Expired PADKOS MACADAMIAS

I bought 4 packs of those nuts at a discounted price yesterday afternoon (14-09-2017) at the store and when I got home I opened one to use it, to be honest the taste was not as usual as the ones I've ate before but I just thought its just my taste buds. A while later after I ate them there was still a bad after taste on my mouth which got me to double check the expiry date, on the discount sticker yesterday's date was written on all 4 packs of which I looked @ even before I bought them, after pealing off that discount sticker on the pack I used, it was labelled sell by 31-08-2017 and after that I was sick to my stomach, I mean why covering the original label with wrong labelling, even if I was going to buy them expired, why hiding the original labelling, let it be my choice, I'm so disgusted and disappointed on what they've done and I'm also intending to take up with company that produces the product and find out if that is the arrangement between the two companies and any structure that regulates such things because people's health might be at risk because of such behaviours.