Prepaid Billing System error - siphoning money

I'm on supercharge tariff. On the last day of my bonus data, I had a positive bonus data balance at 10pm before turning off my phone. I also checked the airtime amount balance.

The next day when recharging i notice R21 was missing from my airtime amount. I contacted cell c service desk and spoke to a supervisor who after 40 minutes of avoidance, admitted that there was something wrong with the billing system of my account as the R21 was taken off for a data transaction at 10:30am but i still had a positive bonus data balance at 8pm ?? I was told it would be escalated to billing dept. as he could not authorise a topup of my airtime and they would respond within 48 hours.

5 days later and still no response. Cell C you have unknowingly ****** R21 of my airtime and i would very much like it back. Please get billing to call me and recharge my account with the amount that was siphoned due to a system billing error.

Perhaps others have experienced this?