Incorrectly billed for data.

On 17 October 2014 i upgraded to a new phone (the Samsung S5). I also upgraded my data for 300 mb per month to 500 mb per month. I now received an invoice that states 01 January 2015 for the date 01/12/2014 - 31/12/2014 for an amount of R886,23 for data used. And the previous month I had to pay an amount of R338.83 for data. All the previous months I did not have to pay 1c for data usage and now, after the upgrade, and paying for a bigger data package I am suddenly being charged for data. The two amounts amount to R1225.06 and I need this to be refunded as soon as possible. We have a full Wifi line at home, thus I am always connected to the WiFi at home and do not use data. I have spoken to Noxolo at customer care and she logged a call for me with the Reference No. 574020. She was very helpful although I have not received my confirmation email that this problem was logged to be investigated. She advised that I must follow up with Autopage in 7 to 14 working days which is totally ridiculous as this is not my mistake. I need this to be investigated asap. I will not let this go and will follow up on this. R1225.06 is a lot of money. By the way, Noxolo advised that i have 1.95G avail??