Contract Cancelled

I paid up the Data contract with Vodacom and i immediately cancelled the contract. But Vodacom kept charging me continously. I contacted them several times to stop charging me but to no help. I even stop using the data but Vodacom never stop charging me. The amount went from nothing to over R1100. <br> <br> I even informed the debt collectors to stop harassing me but they never stopped. <br> <br> Please stop harassing me .