Data Useage

On 29/01/2016 I dialled *111# I still had 480mb of my 3GIG left I received my bill and my data usage is almost 6 gig and billed R1500 over my normal bill this is not the 1st time since December I'm getting these bills I also have a tabled on PAYG on mtn I buy the R89 for 1GIG I use both my phone and tablet the same so how is it possible that with 1 gig I cant even use it up on mtn but on Vodacom 3 gig I go over and as per Vodacom use almost 3 gig in 2 days I called them and was told I must watch my usage and if I got problems I must full in forms I asked to speak to manager and was put on hold for almost 30Minutes then they just drop the call so what must I do just shut up and keep on paying or else get suspended and blacklisted <br> I was also informed that Vodacom are overcharging data and if you don't query its a bonus for them so do we get ********** aswell? or is the next move to get carte balance to investigate