Incorrect debit date & amount

I have recently asked for my debit order to be moved from the 26th of the month to the 1st of the following month which is August. Today I woke up to my debit order debited and an additional amount of R11755 put on hold! Meaning all of the funds in my account I cannot use!!!!! Why would you firstly debit on the 18th before I get paid and secondly why hold more than what is required?! I have no money right now as the person who enforced this hold is unavailable as is my banker and the service centre cannot reverse this! Why would there be only one person to reverse this?!!!! I need cash this instant by my account is currently overdrawn! I am sick and tired of Nedbank's shoddy administration! Your systems are so archaic and only benefit Nedbank not the client! Please return my money and restore my account today!!!!