Vodacom mis selling

I received a call on 4th Feb from vodacom. The agent informed me that they are offering me an extra 10gigs of data on my existing line at no additional cost as a vodacom subscriber. The agent at the call centre was adamant that there are no extra cost which I repeatedly confirmed with her. I was very annoyed onlt to realise That my account was debited on the 8th Feb. I have spoken to two vodacom agents to cancel this service which was sold to me under false pretense but to no avail. I want this to be canceled ASAP. Please can I be contacted. It's experiences of such nature that I would advise people never to do any business over the phone