Delayed report and incorrect info

Cell c called me to say that I owed them over R2000 for data usage however they could not tell me what it was.. I have laid a previous complaint and was called by Daniel who said that my assumption about being called on Facebook messenger was probably the cause. After several calls she said that it looked like it wouldn't be charged but she would get a tech to call me... which never happened. It's probably been over a month and when I check my payment due for the end of this month it's now over R3000. I am furious as this has been left too long and suddenly I get a message to say the data report is ready and I must call them.They should call me!!! I am sick to death of the poor customer service I get from cell c and I am willing to go to court over this. Complete and utter ******* service provider