Over charged for the past 3 months

The internet is good, but I have been getting billed the same processing fee of R249 for the past 3 months, and I have paid it every tim,e and they do not reconcile my account. I have been billed again for this fee. I have paid it 4 times now but it still shows on my account I am meant to be getting reimburt for the over payment instead they keep billing me and now they are treating to disconnect my service but I have over paid. This is pathetic, the consutants do not assist me they just keep passing me around but not solving the issue. What can I do to solve this issue