Can't cancel contract I didn't wanr

Very unimpressed with Vodacom despite numerous phone calls and cancelation reference numbers and promises. They did not cancel the contract that I didn't want. I wanted to stay on month to month but despite this they have renewed my contract and have given me a plan that doesn't work for me. Everytime I phone I get told it will be rectified but nothing changes this has been going on since 7 January. Very unhappy