PnP cheating at the tills

I visited Pnp Kenilworth Centre on 3 Jan to get a few goods. One of the items was a c***** 2L f/cream milk advertised for R29.99 When I checked my till slip they actually charged me R31.99. When I informed the customer service she was not really interested in my dispute. How many of us actually check our till slips or are we too embarrassed to do so, or do we accept that big chains don't cheat at the tills? This is not the first time PnP is guilty of such an offence. If they can do this continuously can you imagine how much it adds to their bottomline? Is this how Raymond and him his family made their fortune? Is this the culture of business we have in this country?