Incorrectly charged for Braai - Builders Warehouse Boksburg!

I purchased a Cadac Gas Braai what was in promotion for R2999 with my builders card. When I got home I saw that Boksburg branch charged me full price R3399. I phoned the call centre and spoke to Vusile and explained the situation - extremely helpful. He spoke to Koleena who informed him that the reason I was charged full price was because I didn't produce a "promotional card" which is BS as I have never had to produce a "promotional card" at builders to qualify for a promotional discount! Vusile then transferred me to Koleena who then told me that I need to come in so that they can do a reversal and then charge me the correct amount. I was told by her that if I don't come in, there is nothing she can do???? Seriously? Why do I have to drive 15km for builders to do the reversal when I paid with my builders store card (apparently they need the original till still to do this). Surely with today's technology this can be done without the client being present. This transaction was done on my store card NOT a credit card so there is no risk.