No feedback from Cell C after promises.....

I was incorrectly billed with data usage (I purchased an extra data bundle and received confirmation from Cell C that it was activated, but was still billed for extra data usage). When I received my statement, I called Cell C and notified them of this. They checked and confirmed the data bundle purchase and time bought. They promised to investigate and get back to me within 24 hours. It has been 4 business days and no response. I called again this morning and was promised feedback today as it was escalated to management level. And still no feedback from them... POOR SERVICE CELL C!!!