Cell C Overcharging Dispute

I have a contract with Cell C for 2 years now and have been out of the country for 4 months. Upon return 1.5 weeks ago, I received a msg stating that I have +300 minutes available and +3gb of data (minutes and data accrued since I was away for 3 month period, with 1 data bundle [1gb] expiring on 1st August, leaving me with 2gb available). This dispute is regarding the data usage... I have been in a WIFI zone most of the time, so hardly any data was used. However, yesterday (6th August) I used the phone data for video streaming and downloads which came to roughly 2.2gb (a figure that the phone's data manager recorded). This morning I received an SMS from Cell C stating that my account will be suspended because if high use. When I called the call centre, Dudu and Heidi advised that I have exceeding my data bundle to the amount of approximately R1900, and that a 50% payment is required to reactivate my account. Firstly, how does Cell C justify approx R1900 when I exceeding the bundle by only a couple hundred mbs? Secondly, I am now left without the usage of my phone and am in urgent need of one - I leave SA tomorrow. I need feedback asap. This is ridiculous.