Standard Bank early debits

I am very disappointed with Standard bank today. Yesterday I got the following sms: Standard Bank: Hi ? for your convenience, your Personal Loan debit order will be processed on the 14 Dec’18 to give you time to enjoy your NEXT family holiday. The Jan’19 instalment will be processed on the normal date. Queries? ***. I phoned them and advised them that I will not have funds available and that they will push my account over my overdraft limit. I was promised that should there be no funds, and there was not, the debit order will NOT go off. But low and behold today that debit order was presented and paid. My debit order date is the 20th...it is not to say that Standard bank pays their staff earlier and on the 14th that the rest of South Africa gets the same benefits! I am royally dissapointed with Standard Bank it feels as it they can do what they want when they want. Why choose a debit order date then? Standard Bank will in any how just take it when they see fit. How is this treating the customer fairly?