Personnel do not exactly know whats going on

I have a Standard bank home loan which gets deducted on the 27th of each month but was suddenly deducted on the 15th during Dec 17 & Jan 18 without giving permission to do so. I personally went to the branch at N1 city and complained and also changed the deduction date to the 30th of each month. Yesterday I received 2 sms's informing me I am in arrears. I phoned and spoke to a gentleman informing me they have no change of dates on their system and it will be deducted on 31 Jan again cause there were no funds on the 27th in my account. I went to print my balance at the bank and saw there was enough money and NO deduction was made on 27th. I phone after a while again and spoke to MARIA to inform her that there was no deduction made and she said they do not deduct over weekends that they still going to do so yesterday or today. I asked her WHY I received 2 msgs then stating that I in arrears and her answer was because they did not get my bond money on 27th. But she just told me they do not deduct over weekends. Who must I believe now cause 2 staff members telling 2 defferent stories and I was not in the wrong and my name being made bad??????? I am not impressed at all and looking for other options to take my bond to.