Unknown costs

I have been with Vodacom for how long now, but 4 months ago my account went to over R2800 for 1 month after I set a limit twice on my account. I then went in to the Knysna branch to change my package to top up, but the amount still differs from July up until recently. I contacted the 082111 number but they refer me every time to their customer care and its frustrating as they dont understand where I am coming from. They contacted me in September to upgrade one of my contracts and advised me that I will pay R109 per month for 4gb data, but October I paid more, the consultant didnt advise me of extra fees as the wifi device has been paid. The same with the number that I am using, my handset is paid up and the amount is still not less as they advised. According to my calculations my total per month now should be R687. Please look into my account as I never skip payments and I really think I am paying too much.