Vodacom: *************, and no follow-through from customer care agents

So Vodacom phones me in January to upgrade my data contract. The lady insists that taking out a whole new sim card instead of upgrading the old one is the best way to go, and repeatedly assures me that I won't pay double because I just need to phone customer care and cancel the old contract as soon as the new sim card arrives. I did exactly that, only to hear from someone else at customer care that I now indeed have two separate contracts and that the other one cannot be cancelled before end of February, so I will absolutely be paying double. This guy doesn't sound at all surprised, suggesting that this is a regular occurrence! He promised to sort it out, and that someone will phone me to confirm. It is three weeks later... no response, no callback, plus they debited my account pro rata in January and again at the start of February for both contracts. Your customer service is an absolute disgrace, and I will be cancelling all my contracts as they run out, because you clearly cannot be trusted with anyone's bank details. I await your urgent response regarding the credit to my account and the cancellation.