Uncancelled contract... ??

I had a contract with Vodacom and when it expired in May they called me to say I should renew the contract, which I refused. I told them to cancel the contract and they continued to renew the contract without my permission. I phoned them again to say they should not continue with the contract to no avail. I am now in arrears and when I phoned to say why they told me to pay then call a certain number for cancelation. This now sounds like a **** to me. I have been with Vodacom for over 15 years and I am so disappointed with this kind of treatment from them.