Misleading Sale - No response when i cancell

Having been called by a sales rep and been told that the package I was being offered would be a add-on to my current Vodacom contract. I accepted. when a few days later I receive a NEW sim card. I queried why I was told that it was a separate contract. I told them to cancel the contract as I was within the 14 day opt out clause I was told there system was down, and they couldn't assist me, this continued for several days. I subsequently emailed them (within the 14 Days) and in writing cancelled the contract to date I have had no response. I am currently being billed for a service I am not using and have expressly cancelled. To say I am angry would be an understatement. I expect a full refund from these people.