Induced to make purchases and then not paid as promised for store reviews

I did a number of store reviews for 4 Pick n Pay stores in Gauteng through the Secret Agent App three months ago in July. The reviews cost me a few hundred rand as I had to make purchases at each store to complete the reviews and I was supposedly going to earn R400, R100 per store. I have not received any payment for the reviews, I have received no reply on my enquiries that I submitted through the App and a Cape Town telephone number I found for them online goes unanswered. It seems that the Secret Agent App is likely a **** to induce one to make purchases at a store that one would normally not make with the promise of payment later, not much different to the notorious Nigerian 411 ****s. I have been a loyal Pick n Pay customer for as long as I can remember and Pick n Pay has always been my grocery shop of choice. This Pick n Pay Secret Agent store review App experience has really left a sour taste in my mouth and my impression of Pick n Pay is very different now. This is my first bad experience with Pick n Pay ever and it's really sad.