Ridiculous vodacom bill

The 1st of this month (July) i get a sms like usual from fnb that says Vodacom debit order is R5706.27 wich is unusual,because the amount that is actually supposed to be debited is about R1300 for all my contracts that i have with them,so the debit order bounced because there is not such a big amount left in my account after all the other debit orders,so i went to my nearest vodacom outlet and asked them about this amount of R5706.27 ,and they said its for alot of data usage,i cant see how this is possible as I constantly monitor my usage of free minutes,data & sms's for both my phone and my wireless data router aswell as my fianc?'s phone,and not one single time did i run out of data on one of the devices,the vodacom mobile application would have shown me if there was no data and so on either devices,of for instance the app did show the bill so far is running up far more than my usual bill i would definitely have done something about it right then,i phoned vodacom accounts department and they offer me a payment method for 2 months for the amount of roughly R4500 per month wich i can't afford at all in any way,if i cant pay those 2 payments my contracts at vodacom will be blocked