PnP overcharging on item on special

PnP is running a special on their extra virgin olive oil since the 25th May (and valid till 6th June). The special is for R89.99 per litre. I was charged their previous 'special' of R109.99 in two different branches. How many customers have been overcharged since then? 2. Where did all the 'smart' people working for PnP go? So they claim that their normal price for the 1l oil is R149.99, although on the shelve it says R144.99(Claremont branch)- but the special price of R89.99 claims to be R50 cheaper than the normal price which would be R139.99. Can they please employ some people who can calculate properly?