Poor service

On April/may, I can't recall correctly. I phoned mtn mondo to ask them to cancel one simcard on my contract because they delivered two instead of one simcard. They said they'll investigate and get back to me. 3 days later the guy really did get back to me and told me that the investigation was in my favor so I don't have to pay cancelation fee. They said the card will be canceled in two weeks time. And now we're nearing the end of August and I'm still paying for the second simcard which was not part of our deal. I sent them an email about a month ago, they then rep**** requesting my personal details, after sending my details I never heard from them again. My reference number was RCO120726