Customer Dissatisfaction

I recently canceled my data contract with telkom which initially was for 1 year. Three years later, I decided to cancel it coz difficulties in terms of internet connection especially where I work. They told me that I have to pay a cancelation fee which I paid. Now these guys just sent me another statement say that I owe the R1011.40 and didn't even state what is it for. I called them, they keep threatening me that if I don't pay, they take me to court.