Vodacom’s Ridiculous Charge

My wife received a bill for her ipad for R7450 and considering that every month for 3 yrs her bill has not exceeded R250 this was obviously a shock (she uses her phone when away from home and wi-fi at home). We went to a Vodacom shop where the customer services person checked the ipad and found her useage ober the period billed for to be 1.7 gigabytes. He lodged s complaint on the system as he said it must be an error. We then received an email from Vodacom saying the charge is correct but they were offering us a 40% discount on the bill because we are such a great customer. Obviously they are incorrect since the ipad measures useage and it was confirmed by the customer service department and my wife rarely uses her ipad. Vodacom says they do not need to tell us what the data was used on and that their system is accurate in measuring the useage! It is shocking how they think they can just bill people and we the customers must accept what they are saying! We are not accepting their offer and plan to challenge them on this bill!!!!!