Handed over to attorneys for closed account

I had a contract with Cell C that expired some time in 2012. At the end of the 24 month period (in 2012) I assumed that my contract would cancel automatically so I stopped paying for it. About two months later I received a call from Cell C saying that I still owe for the contract as it became a month to month contract after the 24 months because I did not cancel it. I accepted that and settled the outstanding amount which was then just above R400. I then asked what I had to do to cancel the contract and the person I was talking told me they would \cancel\" it over the phone. I did not hear anything from Cell C since then. And I thought the matter was resolved.<br> <br> Late last year (end of 2015) I received a call from Cell C's lawyers saying that my account had been handed over as I did not pay Cell C. I was surprised because I thought my contract was cancelled and I did not understand why Cell C did not contact me for the past 3 years regarding this payment and just decided to hand my account over. I explained my story to the lawyers and they said they want proof of payment which I do not have as this happened over 3 years ago. <br> <br> Cell C please sort this out."