Double Billed and no service to fix this

I received an incorrect invoice at the end of April, after trying to sort this out for a whole month, my account was debited with the incorrect amount today. I notified and followed up with Telkom during the whole month of May, although the call center consultants could tell me that they can see that i am being double billed, they could only escalate it to the billing department, who apparently is not contactable. Each time I call in to follow up the response is that the issue has been escalated and that the billing department will contact me. I have also contacted them on Facebook, only to have the same response each time I follow up. To date I have not received one call from the billing department. Telkom's service is pathetic to put it mildly.