Spar giving bad service again!!

Spar at the Reeds once again give me unfair treatment. Today I bought Spar brown sugar 2kg. The price on the shelf said the product is R19.95. Getting to the till paid for our items only to realize on the slip it charged us R38.99. We immediately asked the cashier assist next door to the till we were using.. we asked why the prices differ and she took out a brochure and said it must be on special. The gentleman who helped us said oh yes the special was for 3 days and ended yesterday. I told him on the shelf it said a difference price I bought it because of the price I saw... he just said they forgot to remove it..this was 2 in the afternoon. He then brushed me off. I am a regular customer at this spar but I have recently encountered unsatisfying experiences with management then the staff. I feel like they use bullying people like me who cannot speak for myself even when they know what they doing is not of consumer protection. It is not my first time complaining, just a few weeks ago I wrote a bad review no one attended to my issues. I will not use Spar again if one has to avoid bad service.