Vodacom contract cancelation

It is impossible to cancel our Vodacom contract, they just continue renewing it for us on plans we do not agree on and ignore our request for a cancelation. In 2 years we could not get them to send us a recording and now that this unwanted contract is over they are doing it again, after numerous calls to cancel they say that they cannot cancel and they chose a plan and we apparently cannot cancel???? Now, nothing can be done and we need to call again on 1 June when the new contract that they are forcing on us comes into affect??? Why can't we just cancel the contract, we never agelreed to a lifelong anything with Vodacom, this is just ridiculous!!! People, just save yourselves years of frustration and lots of money by never taking out a contract with Vodacom, ever!