Debit order date

I took out a lone with FNB and the loan debit order date is the same as the date i'm getting paid on. I phoned FNB and asked them if i can change the date and they said yes, with confirmation of a letter from my HR department. I've provided them the letter and now they can't change the date and want to change it to the date specified on my letter. I AM SO ****ING UPSET!!! I'm with FNB and my company with ABSA, my money only clears a day after. If the debit date is the same as when i get paid my account will go into arrears. THIS IS ****ING RIDICULOUS!!! I can not describe the **** level of service i'm getting from the staff i talk to and now this. WHY CAN'T THEY JUST CHANGE THE DATE TO SOMETHING SUITABLE FOR ME!!!!???? i understand the loan is new but common, this is absolutely absurd!!!. Can you please do something or get someone to contact me and explain WHY this date can't be something else other than the date i'm getting paid on!!!!!