Fnb services is bad

I have phoned on 3 different occasions to change my debit order ( fnb personal loan) dates from weekly to monthly due to the fact that I am getting paid monthly now and on all occasions they told me it has been done. It still is going off weekly and bouncing every time. So if fnb cant fix it and give me a refund for the charges then I am going to change bank asap moving my salary to a different bank until they can do it properly.