Disappointed Customer

I took a personal loan with FNB and we agreed that the debit order goes on the 25th as I get paid on that day. When the 25th falls on a weekend we get paid earlier. So one month when that happened FNB took their order from my Standard Bank account on the 22nd. 3 months later they were still running the order on the 22nd and I was being fined by the my bank. I was going through some life changes and never realised what was happening until on the 3rd month Standard Bank called me. I went to FNB to get the issue resolved and noone was taking responsibility at branch level as they referred me to loan division which can only be accessed via the phone. Funny how when you have queries you cant be assisted at the branch but you can apply at the branch. This eventually got resolved after I resend them my pay slip, which they already had, and now this month I got paid on the 24th and the same happened and am now worried if they are now going to be using the 24th again. What irks me is why agree on a debit order date that they just change without consulting me and whats worse is that I have not defaulted repayment since. When I called the loan department I asked the agent these questions and they could not assist and they promised me that their manager would call, which never happened. And to think I was actually considering moving from Standard Ban****