Discovery Health Food Benefit appalling service

I've been trying to activate my Healthy Food Benefit for more than a year. Each time, I attempt to do so, it advises that PicknPay has been selected as my preferred provider, but I want Woolworths to be the preferred provider. I was advised by Discovery to call Woolworths and confirm my details with them, but this has made no difference. I called the Vitality call centre yesterday and spent at least 45 minutes on the phone and was told someone would call me back, but this too hasn't happened. I have also spoken to Discovery Bank people several times and they too are unable to resolve the problem. Please advise