Irregular fee not only charged but taken from my bank account

1) I acknowledge my error - I had insufficient funds in my account last month and the debit order I have with Vodacom was returned unpaid. In all my years as a customer this is the first time this happened and I paid the full amount the following day, on 26 June.

2) On 11 July received an email saying my account was in arrears. I rep**** and attached proof of payment. I received an automated email asking for authentication, which I supp****, but my email went unacknowledged.

3) On 19 July I received an "outstanding account warning letter". By now I'm frustrated because a) I've paid the account, b) Vodacom has not responded to my email, and c) my data account has been blocked.

4) On 24 July I contacted the call centre. In a call lasting an exasperating 24 minutes I was asked to repeat my story to 4 people. Eventually I was put through to Dezlyn, a supervisor in Subscriber Collections. I was informed that although I'd paid the outstanding amount I now owed an additional R100.88 penalty fee!

5) At no point prior to this was I aware that such a fee existed. In both emails Vodacom sent they didn't have the courtesy to explain their policy. In my opinion this "collection fee" is highly irregular.

6) I informed Dezlyn that I had not been made aware of this penalty and I was not willing to pay it. Subsequently on 25 July I noticed that Vodacom unilaterally decided to debit my account with this penalty fee. Other than the debit order amount, I have not given Vodacom permission to take any additional money from my account and this leaves an extremely bad taste. I have been a customer for years and do not appreciate the response I got from Dezlyn, nor Vodacom's strong-arm business practise.