communication not received disgusting service

I have a contract with Vodacom for the past three years now and signed a debit order to go off on my account on the 20th of each and every month ,but in September they tried to deduct a debit order on the 25th of which there was not enough funds on my account and I haven't received any commutation that if the debit order didn't go off that the cell phone will be blocked and when I made an enquiry regarding the debit order that was not deducted on the 20th I was told by khabonina Sibanyoni that the 20th was on the Sunday ,I don't care that the 20th was on Sunday ,is not the first time that the 20th is falling on a Sunday and I know that the debit order will be deducted on Monday ,why this time the debit order was done on the 25th I need this thing to be sorted out and the phone to be unblocked because my sister missed an important interview today of the unprofessionalism of vodacom