Complaint about Simba

I bought a box of salted peanuts, raisins & sweet chilli bits which contains of 24X50g, not sure of the exact date but it's about 2-3 weeks ago from now. Today when I opened one packet I found a pink tablet inside, I called the Simba hotline and I was told that they will come collect the box and do investigation. The thing is I am worried that if they come collect the box they might cover their tracks. What I would like to know is where exactly can I lay a complaint except from Simba.