Difficulty ending contract

I opened up a contract at vodacom stores during June 2014. Debit orders came off from the start of the contract. I called vodacom during January of 2016 to say that I want to cancel contract. I was told too early to do so but could call only in May 2016 to cancel my contract. I was told it can be cancelled in May and my last debit order will be during May. I have the email as proof that vodacom employee confirmed this .So at the start of May I now want to cancel and I am told my last debit order will be End of June. How can this be so? I've even had the phone pit down by a call centre consultant and had over an hour wasted on the phone. I want this cancelled and moved to prepaid. Call me to discuss, seems social media complaints are the only place where this gets addressed.