Refuse to Pay My Own Money Back

A Few Months ago someone at Cell-C duplicated my account. After they discovered it was a fault on their side they promised me that it will be fixed. There are a balance of R616 due to me of that I owe them R189. I have ask them to deposit the money back into my Savings Account and they promise to do so, but is reluctant to do so. My Debit order for the month is R189 and if the is excess usage on the contract it will be added to my account. Since this account was duplicated I hardly ever use this phone so the charges was constant at R189 per month. They send me a sms to arrange payment on this account or it will be suspended. I phoned them immediately to arrange payment and told them about the problems an this account. They agreed that it will be fix immediately but the very next day the line was suspended. After complaining for more then a week every day, they agreed to activate the line and is now telling me that this account is all square as they have deducted the R189 from the R616 and the balance will go to the excess usage on this account. Knowing that there was no excess usage on this account they refuse to send me the billing statements for that period and reply to calls.