Incorrect payment amount paid due to incorrect app amounts

How the hell can this mtn app tell me my account due/bill is less than supposed to be paid. Like an idiot i paid via paygate now you suspend my calls. I have a contract in question, and a pay as you go number since 2001, i spend +- R1800/2000 pm on airtime no points. Update your app or system, because my fnb offers me deals as they see what i spend.