Arrangement for change of debit order

I changed my debit order date 9th of May to last day of the month and today I received sms reminding me of payment. When I called in they said no arrangement was made and I will have to pay the bank charges. Team leader was available to speak too and Lucinda said most probably he will get back 2 u tomorrow. This s unacceptable that I should suffer a loss bcoz somebody didn't do there job