No assistance when my account is overbilled

My account statement had errors where they overcharged my fees, I then called them to try resolve the issue, the lady then said it will be resolved and then I later checked my statement and it was still the same. I then went to the financial department where they told me it might be a module issue that I must've repeated but I never repeated any module. They then send me in different departments within the campus and none of them could not assist. I then booked an appointment with the principal and the problem was resolved but when I checked my statement a few days ago it increased and they have credited and debited some amounts. I then decided to try get help from the campus in Braam where the lady explained to me what is happened and she then called Jeffery at the Pretoria campus and he said he will look into the matter and I should call on wednesday I called on wednesday and he hasn't answered his phone.