Telkom's service is pathetic

I have logged an incident on the 04.11.2015 case number ***7 regarding my invoice I received for over R900. I was called on the 17.11.2015 and they reversed my money, I called in again on the 04.12.2015 when I recived the same invoice amount as I normally do, and the call centre agent advised me that the previous case is still open and that they will just enter another note on the syaytem and that they will give me a call on the 18.12.2015, up untill now I have not recieved any call or feedback. I am sitting with this invoice and my debit order is on the 25.12.2015. My contract has been cancelled on the 15.12.2015 but I am still sitting with my november invoice where I was incorrectly billed. Each and every time I have to call the call centre but they just logg notes to the case. I am so frustrating and don't know what to do anymore. Can someone please get back to me regarding my November invoice and sort it out asap. I would also like to know what my December invoice would be as my contract has been cancelled.