They refuse to refund credit balance

The Multichoice accounting system and billing processes are broken. Check your Multichoice invoices.Very carefully. I suspended my account two years ago. In July last year my invoice reflected a credit balance of R1875. Two weeks ago I asked them to cancel the account. They told me I owed them R620. I told them that was impossible, since the account was in credit when suspended, and no charges should have been incurred since that date. I asked them for invoices since that date and noticed that they had reactivated the account without my permission, hence the charges. When I queried this, they adjusted the account so that it now reflected a nil balance,but I pointed out that the balance should in fact be in credit (as reflected on the July 2015 invoice) and that I wanted the credit amount refunded. They disputed that, despite the evidence of their own invoices and statements. I am still fighting with them. They cannot be trusted.