Interest charged on a 6 months interest free account

I called two months ago to query the numerous interest charges on my account as I have a 6 months interest free account. I was advised by the agent that all my purchases at Jet since last year have been incorrectly allocated to a 6 months revolving account which incurs interest and not the 6 months interest free account. The agent advised that she will request the team leader to reverse all interest and charges for purchases from last year that was incorrectly allocated to the interest bearing revolving account and that my February statement will reflect the credit. To date this has not been rectified and I am still being charged interest. This is so frustrating as all the small amounts add up. I am actually thinking of closing the account.