Wrong billing.

I received a call November last year, they sold me a router, I took the contact using my existing number, when they delivered the router,I called to tell them I received it, on that call that's when I realized I will forfeit a lot of benefits, e.g all my incoming calls will be on private, I will no longer have privilege to buy free minutes, that's when I took a decision of cancelling the contract with my current number. The consultant advised I can cancel and take it again on a knew line. I did cancel same day of delivery, they came to pick up the device the following day, but after that, there's Still loaded data on my sim card, I called, I then called they told me it will be cancelled and they will take the data away, they debited R116 I called they said they will refund, I waited till I reversed the money, I called asking with the little data used how much am I owing, they said R379, on a contact of 30 days for R199 and I used little data for 2 days how does it add up to R,379 , also why did they still load data even if I had cancelled the contact. Why? Really disappointed on the service and the unfair billing. Why give me data on a cancelled contact next thing it's an unfair billing. I've logged a complain since last week no response .