6 months interest free account changed to 12 month

In December 2014 i opened an account with RCS through Sunglass Hut in Hyde Park. My application clearly indicated that it was 6 months interest free. I bought for R3884.00. On the 15th December the debit order was half of what I expected and so was the one for January. I called the call centre and informed by the agent that my account was captured as12 months. After holding on for a long time while he said he was referring the matter I was advised that the matter had been resolved and i would pay the balance over 6 months. On 15 February the amount was far less than one deducted previously and same happened in March. Today I again called the, and was advised that the account has been changed to a revolving or open account meaning that I can buy whenever I want. I again told the consultant to rectify that and he also advised that he had made a note on the system. Imagine my surprise when he told me that my balance is R3500 +. This for a purchase of R3844 and which i clearly indicated that it should be deducted over a period of 6 months! Is this a scheme to make money or what? I am so disappointed and regret even buying on credit.