All i want to do is change my debit order date!

I have requested to change my debit order date to the 1st of the month for my Revolving Credit Plan & Smart Spend Loan. I requested this through my Premier Banking and got a call this morning and was put through to Loans department and now was told i cannot change the date till i get paid at the end of the month and then phone back or send a letter from my HR department. All i want to do is change my debit order date, it can't be that difficult. i need this sorted out.