Wrongfully Billed

I have 3 phones with Vodacom, which I am paying them in time and always keep my limit but now I have just realized that my Laptop account is owing R2981.92 for data usage and funny thing is that I have been using this laptop for over six months and the amount were stable. I get 1GB every month and I don't even use it regularly because most of my time I am at work and now I am very much surprised that I am owing this much of amount, please look at my statements below :<br> November Bill 2015<br> Description Amount (excl. VAT) VAT (14%) Total Amount Amount (incl. VAT) <br> 1GB MBB 24 month - Contract November R 65.79 R 9.21 R 75.00 R 75.00<br> 3G LAPTOP INSTALLMENT R 192.98 R 27.02 R 220.00 R 220.00<br> Content Services R 8.60 R 1.20 R 9.80 R 9.80<br> Data Usage R 2347.65 R 328.67 R 2676.32 R 2676.32<br> HSDPA Voice Tariff November R 0.00 R 0.00 R 0.00 R 0.00<br> Total R 2615.02 R 366.10 R 2981.12 <br> OCTOBER BILL 2015<br> Description Amount (excl. VAT) VAT (14%) Total Amount Amount (incl. VAT) <br> 1GB MBB 24 month - Contract October R 65.79 R 9.21 R 75.00 R 75.00<br> 3G LAPTOP INSTALLMENT R 192.98 R 27.02 R 220.00 R 220.00<br> Data Usage R 0.00 R 0.00 R 0.00 R 0.00<br> HSDPA Voice Tariff October R 0.00 R 0.00 R 0