wrong contents in capsules

I bought a product called "Relax" (melatonin) by Biopharm Technology from the One Life Health Shop in Centurion, and the capsules did not contain melatonin. The packaging's plastic bottle had changed from white to black, but the label and content's description was the same as before. I have been using melatonin for my disabled son for several years to help him sleep (prescribed by his neurologist), and had been using this particular brand for more than a year. When I gave my son the "Relax", he didn't sleep at all that night. I noticed that the capsule's contents was different from before- darker in colour, and the taste was bitter, but I thought it was perhaps a different filler or by product used, so I gave it to my son for another two nights. I tried a capsule from the other bottle i bought as well, but he still didn't sleep. The following day, I reported it to the health shop, and asked that they give me feedback. When the health shop called back, they said they spoke to the company, and that the company admitted there was "definitely something else in the capsules". I asked if they could please give me feedback as to what it DID contain. Several days later, I returned the products to the health shop, and asked for feedback. The health shop contacted someone from company while I was waiting there, but the person I spoke to refused to comment. I wasn't told who i was speaking to or what capacity they were. The man did say that they would get back to me, as I asked for feedback. After a few days, I emailed the company, and also filled in a web-form, asking that someone contacts me. It's now been about a week, and no one has contacted me, or even called to acknowledge the incident. This could have been potentially extremely harmful to my son, and I still want an answer as to what WAS in there! I will NEVER support that brand or that health shop again, as they also didn't take any further kind of action (other than removing the batch from the shelf). To make matters worse, the assistant imp**** that I was to blame for giving melatonin to a child!! I think it's utterly poor how the company handled this (simply ignoring me)