Cancellation of contact due to misinformation given by to customer.

I took out a mobile contact with Telkom over the telephone and was mislead by the salesperson. After receiving a large bill in the first month I decided to cancel. I submitted cancellation forms a number of times and spoke to customer care about progress also numerous times but I have been ignored. I have written a letter to Telkom and still got no response. This has been going on for the last 9months.