POOR CELL C CUSTOMER CARE

Still the same issue, my contract was cancelled about 2 years ago, I received a statement after a year claiming that I owe them an outstanding amount, about 2 months of premuims, I had an arrangement to pay R100 a month. Which I did. I send emails to confirm from Cell C's side if everything was paid up. I received no reply after a few mails without replies I gave up. Almost a year later I checked my Credit report and I saw that I still owe Cell C R100.00, Again I tried to call with no luck and send another mail asking them to se d me an account number where I can make the R100 payment. No Response. I reveived an sms to urgently pay Cell C R1378.62, I would like to know how they got to that amount from R100.00 and without notifying me that the outstanding R100.00 was not paid.