Vitality Healthy Food Cashback

I normally get an average of between R650-R750 per month. On the 02 Feb 2018 I received a R52 cash back from Discovery Vitality, which is incorrect. I've called this company many times and their lack of investigation, feedback and concern is the worst I've ever received. I feel like a nag because I've given them all the facts proving that the payment they made into my account is R700 short of what they should have paid me based on the download on their website under my username of healthy food they should have paid 25% back to me. I've spoken to numerous call centre agents who promised to either return my call or managers this call has been referred to which haven't bothered to call me back. I spend a huge amount on groceries every month and I spend lots of money on healthy food because I get this benefit and coupled with the fact that I have to pay the monthly vitality fee of +/- R320. This is by no means a "cheap" benefit. The least discovery can do is pay me whats due and yet they are brushing me off. I've had enough of this sub-standard service and expect someone to pay the money they owe me and a written apology. I've given them all the info they've required and they still won't pay me the money they owe me. I find all the people I've dealt with at Discovery to be lazy, condescending and unhelpful. I feel like I'm being a nag. I want this problem resolved immediately. Its been two weeks.