Unhappy customer

I am very disappointed with Vodacom, I upgraded my contract with them and thought that things will be smooth as it was. I recently changed banks and as we all know you have to notify your debit order in order for them to debit successfully and I did that. Now, what they did they debited the incorrect account and the debit order bounced now they told me that I have to pay an extra for the bounced debit. I told them to go listen to the call when I changed the account details and they said they would I should give them 7-14 days of which I did and guess what I didn't get any feedback, then I got a debit order from them of an absorbent amount and I call them again and they told me the same story of 7-14 days and I said I'm going to wait and give them another chance but they did not do as they promised. So I would like to get feedback on my query before I look for someone who will want to service me the correct way.

Thanks