Unresolved account issues

I had to move my contract from my mothers name unto mine. All went smoothly, or so I thought. When I got home and checked my Vodacom App, I saw that my bill was almost at R4000!! I have a Red VIP+ Contract, the amount is set at R2100 and for my handset I also still have to pay which is R400 something a month. In normal circumstances, my bill ALWAYS amounts to R2500 never more. When I tried to go to Vodacom they told me unfortunately they can't debit my account because this is done only by the accounts department. I phoned the accounts department but to no avail... They told me that they can't debit my account! How is it possible to credit an account, but not debit an account?! This is basic accountancy!! Vodacom told me that someone had made a mistake by saying that I did an upgrade and not a name change, so you guys charged me prorata for December. How is it possible that when you make a mistake I have to sit with the consequences?! You are "unable" to help me! In January it still went off on my mothers account, they only took of the old amount. This month however, it started going off on my account and took off R3 940.81 which wasn't budgeted for and will now be affecting me negatively. This is unacceptable as I have tried to sort this out for almost two months now, no one has been of any help and now I am sitting with something that is actually YOUR problem.