What is going on, I need to be refunded!!

From February 2014 my 2 year account which was 5GB at R499 a month ( + handset and landline ), suddenly jumped to anywhere between R900 & R1500 per month. I was told, by my statement, that I was going over on average by an additional 8Gb a month. I have numerous reference numbers & no actions. My contract expired in June 2014 but due to the fact I have no answers to the increase cost, I needed to sort it out and hopefully get refunded. I was told if I close the account, any further action or investigation could not happen to solve the matter - I kept it open for another 8 months while being billed way over my contact amount. I was lead on month to month for these 8 months regarding the 'investigation'. <br> <br> In March this year I decided to try again - this was invane! To change my numbers etc is a cost so I went to the store again & was assured if I took out a 15GB contract I should no longer have problems. My monthly statement now tells me that I'm using around 20GB. How do I use more data if nothing has changed regarding my usage. <br> I work in a studio on my own with a secure password.I have had a IT specialist confirm that this usage is impossible for my day to day business usage.