credit agreement violation

remind me again why i bank with this bank, i have a loan with them and we agreed they must debit my account on a certain date, however as soon as there was money available on my account they debited it , i phone customer care and first consultant who took my call did confirm that the funds were not supposed to be debited cause its not the agreed date, she transferred me to the credit department and a certain siyabonga answered all he did was give me attitude about not reversing my money because the funds reference says Salary i told him this is from a claim and work besides that our agreed debit date is the 25th because i get paid on the 25th he continued to give me an attitude telling me i must go to the bank with a letter confirming the funds are not my salary but i claim is he out of his mind , they debited my account on the incorrect date why must i go up and down due to their fault violating our credit agreement , what a useless bank and its consultants,