Overcharging for items at till

I recently visited Builders Warehouse Cape Gate and got a little surprise when paying for my 2 items at the counter. First item marked price in store was R48 - amount charged was R65 Second item marked price in store was R54 - amount charged was R58 I am dumbfounded that both items I wanted to buy were incorrectly charged. I always pay attention to detail so that I don't get ********** ... but how many others don't check what they are charged and have been ********** by Builders Warehouse? This is an ********* business practice. They did at least refund me and charge me correctly second time around.