MTN Upgraded the contracts I wanted to cancel

I have allowed three of my MTN contracts to run their full term because I want to cancel them. Sadly, our MTN signal strength is not great, and I've had one or two snags with MTN in the past which I wasn't happy with so I decided to move my business elsewhere. I went into our local MTN store and was then informed that two of my contracts had been upgraded already. I told them I had not asked or signed for anything. I've struggled to get hold of someone who can explain what has happened at customer care, so I complained on Twitter. They said they would get back to me. Nothing. Now I've opened my bill and where my average spend (all capped lines) is R629.45, this month I am going to be debited R2396.97 (3x R798.99).