Account changes

Headache so early in the morning. I requested for my account details to be changed to a different bank account and I asked the agent Nothando when will the changes be ineffect and she said the following month which is end October. To my surprise end September the new account was debited and it doesn't have funds yet, so the transaction bounced. When I called in both the agents I spoke to after explaining my issue they put me on hold and the call disconnects. My issue is that I do not want to have a missed payment! Such an inconvenience because now I have to go to the store during month end to sort this out!! Really unacceptable.