Cell phone contract cancelling.

I have four contracts line with Telkom of which the fourth one contract has expired and Telkom renewed it without my concern. I have tried several times to cancel it via telephone but with no luck. I called client service several times, went to their store in Greenstone and they always give me the wrong information. Kindly assist me by cancelling this line ***( Free me 1 GB) as they billing every month for something that I don’t use.