Continuously over billed

I renewed my Telkom Mobile contract in September 2015. A month later I realise that they had opened another contract on my account and were billing me for it. I was over billed around R2400.00. It took Telkom 4 months to sort it out. On the 28th of Jan 2016 I get a message to say I will be billed for R5733.84 for the cancellation of the contract I never opened. The service and the delays from Telkom are atrocious and I would never want to deal with them again if I could help. They just take money from your account as they feel fit to do. And there is never anyone to help you sort it out. You must just accept this bad service.