Impossible to change debit order date?

I have a personal loan with FNB and the debit order for this loan is the same date as my salary payment date. I recently changed jobs and my salary payment date has changed to a later day in the month. I would like to update this debit order date as it may get debited with not enough funds left in my account.

I have been trying to get this date changed for over a month and have had no luck so far. I have tried phoning the relevant numbers for someone to assist. I get transferred from one number to the other until I end up on hold for 20+ minutes. This consistently happens until 16:30 where an animated voice tells me I am calling outside office hours and should try again tomorrow. Just to try the next day to go through the same issue. I have spent so many of my minutes it is ridiculous.

I thought maybe going into an FNB bank and talking directly to a FNB consultant would help. The consultant sent an email of to some FNB email address. Till this day I have had no response or feedback. This email was sent on the 17th July 2017, today is the 18th August 2017.

Is this the service FNB provides to its customers? What is the point of having Premier Banking but its of no use to me?

I am highly fed up at this point!! I would like to get this date changed as soon as possible because if there is not enough funds in my account at the end of the month I will have to pay the penalties and face the consequences for your pathetic service!!!! This is unacceptable!!