Incorrect Billing

I have a premium price lock and been pay R1008 for the past few months, however end of August they debited me more than the installment. I called their call centre and i was told it was an error and it will be credited back in September. To my surprise in September again the debit order was incorrect. I call in and the recipient did not know the reason. I was put on hold for 20 min and the line cut. No one called me back. The following day i call again and the lady put me on hold for 30 minutes... Until today my issue has not been resolved.