Debited for data, when I have a top up contract

A few months now I have been getting statements saying am in arrears.I sent4 emails to Acc over this time to query,with no reply.I went to the Mtn Umhlanga Ridge&they confirmed on3separate occasions that my account isn't in arrears at all.Last month I saw on my bank account that I had been debited just overR 2 000.00which I know is impossible as I have a top up contract so it is a fixed debit order amt.I opened my contract in 1998&have always had top up.My 2contracts were up for renewal Nov/Dec2014 which I upgraded,1 on the same package, the other to a lower package.On top of this I had such issues with the upgrade I almost closed my account.I called the call center&the lady said that 1contract was not on top up so thats why I was charged so much&it was for data.I told her I would like a copy of my contract but still waiting a week later(also emailed 3 times requesting this&keep getting my statement)I have looked back&been overcharged a few times.What gets me is,I don't have FB, emails&hardly any apps on my phone to use data,I basically only use Whatsapp&have disabled most apps.Even funnier I turn my data off every night around 7pm.I havent given permission for these debit amounts!