For bad service call Cell C

I have this issue with Cell C where I canceled my contract on time but was told that I still owed them an amount of R285 that didn't make sense to me because my contract was only R99pm I only made my contract into a prepaid. Cell C decided to hand me over. I asked Cell C and the other company to send me an email with the details because I am taking them to the ombudsman I still haven't received anything from anyone of them. this morning I phoned Cell C customer call line and told the guy I am trying to pay my account on the FNB app but I don't know what reference number to use, he asked me security questions: my name, ID number, and from which bank are they debiting me from, and according to him I got my answers wrong and should phone back with the correct details... how do you get your name and ID wrong!!!!