Even more uselss Vodcom

Took out 5GB data plan. Realised I was not getting what I wanted and cancelled well within the 30 days cancellation period. Router was picked up by courier company and the contract was cancelled on 30 August (or so I was told by the call centre operator). I was still billed for the cancelled contract end of September. Could get nowhere with customer care as they said the contract had not been cancelled (as I was assured by the same customer care that it was). Complained on hellopeter and suddenly Vodacom was very happy to be helpful. I was called back and after long fight I was assured that the contract was now cancelled and I would be refunded the money that they wrongly billed. The money would be paid back into my account within 7 to 14 working days. A week later I was called by the same person asking if I would be happy if they rather credited my account with the money they owe me, rather than paying me the cash into my account. I accepted this offer. Today I find out I owe Vodacom more than R3000, according to them because I cancelled the contract prematurely. It was cancelled well within the 30 day cancellation period, and it is only because of the uselessness of Vodacom that it was actually really cancelled outside this period. I refuse to pay for Vodacom's utter uselessness