What you see is not what you pay

What a major disappointment. Bought 2 x20 F/Earth Severe weather on the 11 Sept. Pay price what was R 899 and got my 10% discount because I am a pensioner. When I bought another 20 Lt on the 18 Sept. Price still R 899 - but when you go to pay for it they load it as R 929 and not R 899. Reason they say because according to them this is on special. QUESTIONS: Why is their a price different from the previous week? Why is the "special" not loaded as a SPECIAL on their catalogue. I have tried numerous times explain to the manager - show me where is this listed as a special, but she did not even care to look and just walk away while I was still talking? LAST TIME for me at BUILDERS. I hope Chamberlains close them down