administrative incompetency cost me

i changed jobs and therefore the date of my salary being deposited changed. I informed Wesbank via e-mail and asked for the debit order day to be changed. I got an e-mail back informing me that it had been done, to my surprise in January my account was never debited and on the 30th it was handed over to a collection agency. Mind you i had money in my account I then think the matter is solved when i was informed that a manual debit order would be done. To my utter surprise Wesbank debited my account R900 more than the usual. That has left me broke and I wish to know who is to blame for this. Everytime i call i get directed to someone who points the finger at someone and till now it has not been resolved. Now i am the one who has to fax bank statements proving that i had money in my account. These people at Wesbank are giving me all kinds of excuses. Can somebody who knows what happened tell me why and how this happened. R900 is a lot of money and i will not let this go so easily.