Debit order taken before the salary was paid

I have a personal loan with Capitec bank and the agreement contract is they debit on the 25 of every month or the date when my salary is paid in. But they debited my bank account before I even received my salary and no notification was sent to me. Head office failed to explain why they put a request for a debit order when I haven't been paid. I even submitted my statement to show no salary has been deposited in my account. Why draw up a contract if you do not abide by its terms.