Billing fault

I have a problem with Telkom billing department. They don't debit the money on time. They will not deduct for 2 consecutive months. On the 3rd month they deduct the whole amount for 3 months, whilst my account has always have money on it. And they charge me debit order penalty fees. While it's their fault not mine.

I went to their branch several times. And they said they will log a complaint. I will be contacted within an hour, and I haven't received any call from them.