wrongly bil**** for data

I upgrade in middle September from a Blackberry to a Blackberry Z3, my contract expire only in December so the old contract is still valid. to my surprise when I draw a statement on the 12 October I notice that I was billed for data use while my BIS data remain the same I called Cell C on the 12th October and was told that it takes two days case: *** and someone will call me back I have not received any calls so far I need answers since my debit order already went off and this needed to be fixed, very angry and disappointed with Cell C iam a customer for the past 15 years and this is the kind of service they provide. contract cell nr: ***, they can contact me on ***.