Paying a cancellation fee of R 800 for an incorrect package selected by the call centre agent

I received a call from Rewards co call centre on behalf of MTN. I wanted a R199 sim only deal that I saw on the MTN web page. I app**** online for the contract. Fast forward to receiving the sim card. I had to run up and down activating the sim card. When it was eventually activated, I discovered that an incorrect package was selected for me. They gave me a home fixed package of which I did not ask for. I had to call and make numerous trips between MTN Springs and MTN Carnival Mall. I was adviced to call MTN retentions department and the agent had told me that if I want to cancel my contract I would have to pay a cancellation fee R 800. Mind you, an incorrect package has been selected by the agent but I must end up paying R 800? Someone make me understand! I can't use the sim card in my phone or in a portable router because the account get blocked when its used in an "unsuitable device". At this point I want nothing to do with MTN anymore. This was my first contract with them and I regret this decision wholeheartedly!