Paying for their mistakes

I called a week before my account should be debited to enquire about the amount I needed to pay to settle it. I confirmed with the agent who's name I cannot recall that payment will be made no later than COB on the 17th of August which I did. The agent asked how I would be making the payment and I advised eft. I made my eft transfer as agreed and on my account was debited again on the 25th of the same month. I reversed the amount and they refunded me again. Then I get a call to say they refunded me why was it reversed. I explained that the debit was not supposed to go off in the 1st place as it was settled. I agreed I'd pay back the reversed amount but I can't be liable for the penalty fees as this was an internal error. Apparently their mag tape is sent through 5 days before collection and this was not communicated their agents are ill informed and surely that cannot be the client's fault. I have paid back what I owed but I cannot take the blame for these so called penalties in every call I asked to speak with a manager and its now October and still nothing I'm harrassed with calls for penalties. This is nothing short of *****ing!!!