Wrongly debited

Since December 2014, I have been trying to have my bill corrected as I was incorrectly billed for data usage. I tried on numerous time to speak to the consultants and have several reference numbers with no help. They cant prove that I used the data and I have disputed the amount used. No confirmation or proof can be given, and therefore I cant accept the amount debited. My normal amount is not more than R150 a month and for Nov and Dec 2014 amounted to R 2500 per month. After my complaint again the R 150 per month.