handed over without clearing account

I cancelled both my contracts last year also with a big fight.my sons line ***) last payment was for June 2015 and my line ***) was for July 2014. i remembered i spoke to a coloured lady who helped me sorted out the cancellations and confirmed it was cleared and cancelled. now suddenly i get an sms from Nudebt that i am handed over for R149. NO One form Cell c contacted me last year to say i was still in arrears, but now i am threatened by Nu debt i will be black listed if i dont pay the amount. if this account is not sorted out by Cell C and my name cleared i will take this further with the NCR. your poor service is totally unacceptable and i demand this to be sorted out without me paying anything. i am not scared to take Cell C on with the NCR as i know i paid up my account and it was confirmed to me.