Poor service, failed to change debit order date

I have a personal loan with FNB which has been deducted directly by FNB while I was employed by FNB. I have since moved, I call loans to inform them that they must debit my account directly and change debit order date to the 26th of every month. The person I spoke say I must get a letter from my new employer confirm when is my payment date. I find this request extremely obsurd. Can some who is able change this, this personal was supposedly transferring me to collection but I held the line forever. My ID is *** Contact: ***