Price reduction not app****

I bought 100g Padkos Mandarin Slices at the Checkers Hyper Mayville on 18/01/2018. Original price R38.99. It had a sticker on it that promised: Reduced price 50% off the marked price. When I checked my receipt on getting home, I realised that I paid R 40.00 for this item.

I tried several times to report it on the Online Customer Care email option, but the only result is: A System error ocurred. I am not willing to call the Customer Care Helpline, and holding on for hours since there is an email option.