BILLING INCREASED WITHOUT NOTIFICATION

I have two cell phone contracts with Telkommobile. One I took in 2013 and another in 2014. I want to talk about the one I took in 2013. The 24 month contract for that contract has just expired. All the times for the two contracts I have been paying around 350-360 rands.I had called Telkommobile before the expiry asking about what will happen thereafter and I was told that, until I cancel the contract everything will remain the same (the payments, the data bundles and the minutes)<br> To my surprise I received an SMS telling me that my payment end of November 2015 will be R964.24. No one told me about this before. I never signed for this amount. When I called the callcentre I was told that now I am being charged for what I Telkommobile is giving me. Very funny, because I think they were supposed to cancel our initial contract or advise me to cancel so that we sign a new one. I never signed for that amount of R964. They must please take the bill to the one who signed for it, which is not me.