Huge account but no data received

I received my invoice for August only to discover a huge amount due. Apparently for packet switched data calls. On 25/08 i logged a query with Sibusiso. He sent me a report reflecting the sites utilised. This does not show the cost. On 17/09 i spoke to Rachel (ref ***) who arranged to have a statement with the cost sent to me. Later that evening i spoke to Bongani(Ref ***) as i realised that i might be having the same problem as with my other mtn number. Since my upgrades were done in the same month. He confirmed my suspicions that NO data was loaded for some months. Bearing in mind that when i spoke to him i had 981mb remaining and data for Sept was not loaded yet. How can i owe R1120.86 excl vat if i still have so much data. Data was only ever used in Jul-Aug. Mtn can not charge me out of bundle rates if they did not load my data every month as per my contract. It was only because of my other number that i actually logged another query. I am always willing to pay, BUT not if it is unjustified. Mtn needs to get their act together as since the strike, we have had extremely PATHETIC service. I wont pay unless Mtn can prove they loaded my data & their billing is correct