Debit order cannot be changed

I called the call centre today on the 23rd of November to find out WHY they debited my account 2 days before my debit order date. The debit order returned and I incurred HIGH bank charges. I then requested to CHANGE my debit order date to ensure this does not occur again. I was told I need to get a letter from my HR. WHY do I need to get my HR to draft a letter just so I can have my debit order date changed? This is ridiculous! Shame on you FNB!