Lack of interest over account overpayment

At the end of October DStv (MultiChoice) debited my account with almost 3 times the amount of my monthly debit order. It took a couple of phone calls to get them to agree to correct the problem and they credited me but they short credited me almost R1000. I have tried countless times to try and speak to someone to get this account sorted out and nobody can help me. I am only able to talk to call centre agents and nobody from the accounts department bothers to contact me. This is a complete lack of interest or concern on their part over a mistake that they have made and shows how little they value their customers.