I can't seem to get a correct amount from them or even any assistance,,,

I upgraded my package in December and soon after my problems started,,, I was given a crazy amount to pay on the self-service portal and I called and was told to pay R70 as the prorate and I did and was told it will fix itself by month end before my payment was due and come the time it was still the same and I downgraded and was to pay R299 and I did .. the package is still same and I'm still being crazy billed and today I called the lady says her system gives her an error when she wants to check how much I should pay,,if my account is disconnected coz of their nonsense,, should I now pay for other people coz I'm double billed as per what their consultant said,,,I'm almost fed up, infact gatvol