DEBIT ORDER PROCESS IS RIDICULOUS

I need to change my debit order from the 27th to the last day of the month. The person who I spoke to on the phone informed me that I would be able to do this but it would only take effect from the following month. I have changed jobs and therefore my payment date has changed to the last day of the month which means that come the 27th of September there will not be sufficient funds in my account to make this payment.

Surely this is the most ridiculous thing as if I am still ensuring that the money will be paid for this month but only at a later date? She then proceeded to insult my intelligence by trying to explain to me how a debit order works. Seriously hate complaining and try not make a habit of this but this is just ridiculous.