Incorrectly charged R4500.

I have a tablet contract that comes with 1 gig of data. I never ever go over 1 gig and in case I should, I have a Data Limit of R1500.<br> I always monitor my usage via the MTN app provided on the Playstore and MTN are the publishers.<br> <br> My usage is normally around 400mb and 500mb per month. I've had this contract for 20 months and have always been billed R399 (the contract price). <br> This month, I get billed R4500. Apparently it is because of me exceeding my data usage. I have the app to approve this is not true and with a Data Limit of R1500... I shouldn't be billed anything over R1500 + R399 R1899.<br> <br> I have called the call centre agents several times and the call mysteriously gets cut. I've spoken to 2 team lead of the call centre, nothing. <br> The accounts department sends me a break down of the data usage which is wrong, I reply and still haven't got feedback.<br> The twitter entity gave me the same break down, and again no response after my reply.<br> <br> Who do I escalate to? Which person? Don't tell me 808, useless.<br> <br> What now MTN!