Pick n Pay Express Excessive Pricing

Logged an online complaint with PnP on Friday 22/01 , no response as yet and very unimpressed by the fact that they just don't care if a customer is unhappy. Current price on promotion at PnP for Sprite zero 2L is R13.50. I purchased a couple of bottles from my local PnP at this price on Wednesday. On Friday decided to get two more bottles prior to weekend. Not wanting to go into main PnP, quickly stopped at PnP Express shop nearby. Was shocked to find that price was R21.50 a bottle! Apparently my understanding that PnP and PnP Express would have similar pricing structure is incorrect. Even if they didn't have special and charged R16, would have been acceptable. You pay extra for convenience? Really? 60% more is excessive. I know if I shop at Spar, I expect to pay more but there price is just under R16.