Contract paid up but still billed after cancellati

On 18/08/2015 two contracts I had with Cell C were paid and the proof of payment was sent. I called them for cancellation, since then I did not receive any calls from them, in my terms this meant everything was well, contracts paid up and they were cancelled. <br> <br> Today 09/02/2016 I get a call from them telling me I'm owing? Owing??? I was a bit confused as to how can this happen. Why did they keep quiet for such a long time after I paid them? They asked for a reference number I got after cancelling the contracts and mind you that is almost 5 months after the contracts were settled. They were not getting any money from me for the whole of 5 months and they expect me to keep the reference done 5 months ago?<br> <br> I've always heard from my friends that when the contract is paid up with cell c, one needs to call them for cancellation which I did because I was avoiding their billing which does not stop even after the 24 months of the contract is finished. I've never been happy with cell c from the beginning cause of their crazy billing system even when the contract is top up. <br> <br> What's worse is that those numbers I was using were closed long before being settled. Won't recommended cellc to any1