Incorrect amount billed

On the 7 august 2015 i received a bill for an excessive amount of R2126 billed for the previous month on my data contract which is impossible since i hardly used the modem myself and all my previous bills for this data contract have never exceeded R140 , the months after receiving the bill for R2126 i then received a bill for R817.70 after requesting an investigation and itemised blling documents after the first amount but with no feedback, im still waiting for mtn sp to get back to me on it (ive been waiting for a response from them from 7th of august 2015) and have contacted them numerous times and still no feedback, their service is horrible as they have incorrectly billed me before as well a year ago, i would not recommend anyone to use mtn , since a lot of people that i know are also experiencing troubles with mtn<br> <br> after this bad degree of service i recieved from them i have blocked my modem so that no extra charges can be made, i all the contracts i have at them have been suspended since since it feels like they refuse to resolve this situation