Unauthorised debit order

I have been with Wesbank for only two months, we had an agreement that my account will be debited on the last working day of the month. This month they decided to debit my account on Saturday 28 March, cleaned up my account and left me with a negative balance. Surely everyone knows that the last working day of this month is Tuesday, 31 March and that is when my salary will go into my account. Wesbank have created such a mess for me and this must be fixed as soon as possible before I escalate this further. They have caused so much frustration and inconvenience for me and my family this past weekend. I do have other debit orders but I have never experienced such unprofessional, ********* and pathetic service from any of the other financial institutions that I have done business with! I am really disappointed with the manner in which you conduct your business and I hate to admit that I was never comfortable with my vehicle finance being handled by yourselves from the very beginning and now you have proved that I made a terrible mistake by signing a contract with you. I will never allow Wesbank or any other institution to control my bank account and do as they please.