MTN Collusion with RewardsCo

I received a call from RewardsCo on behalf of MTN regarding an existing contract I have for a data sim, which I am paying R400 pm. They offered me a new deal for an uncapped LTE router for R340; R60 less that I am paying for the sim data. No brainer right? Take the new deal on the condition that my old one gets cancelled? I told the agent that I can only take the new deal if they cancel the R400 contract and I was assured that's what will happen. Unfortunately that was not the case and now I am being told by MTN that there is penalty for the cancellation! What frustrates me the most is that MTN partnered with RewardsCo, sharing my personal details with them so that I could get spammed with phone calls regarding new deals leading to sales for MTN and commission for RewardsCo but in return leaving me with penalties for cancelling existing contract. I logged a case at beginning of this month with MTN but no one bothered to call me for updates. It is month end now and I will be required to pay 2 contracts!