Cell C
Customer Service doesn't respond to overbilling

I have a Cell C swoosh 3g. The contract was for R300 per month for 5gb per month.
Now I've been cutt-off and owe over R2700 for two month's worth of data.
I went to a Cell C, they said phone the call centre.
I phoned the call centre but due to high call volumes I had to send an email to customerservice@cellc.
I mailed them on Monday, I recived an automated response saying they would contact me within 48 hours.
I've been overbilled, and I can't seem to get hold of anyone.