Faka I klipa - promotion

Hi Multichoice did a promo called faka I klipa which I took advantage off and paid R100 to get the promo instead they changed my subscription to compact and charged me more than the R100 promo now I have phoned and visited their offices several times but they refusing to credit me with about R123. 00 that they overcharged me, I never sent them anything to say they must change my easey access subscriptions. Please help