INCORRECT BILLING FOR DATA

For the past 18 months, since my upgrade with Altech, I have never paid for data and never paid more than my monthly subscription of R577 pm. Suddenly in April I have data costs of R1 223. In previous months I have used more than a gig of data with no charge. The month before was 1.7 Gig with no charge. Why now suddenly? According to the callcentre 2 weeks ago it was a billing error - still waiting for this to be reversed. I refuse to pay as I can't afford it. Obviously they threatening to suspend the line. I see there have been numerous reports of incorrect billing on the site. I hope they can get mine sorted and prevent this from happening in future. The Kenilworth branch was absolutely useless and didn't even log a report.