Incompetence at its best

I contacted Wesbank to request to change my banking details for all four of my accounts that I have with them, they said they would send me a form that I would have to fill in in order for them to change the bank details. They sent me the form and I proceeded to fill this in, by account no. I put all 4 of my account numbers separated by a slash (/). I sent this to [Email Removed] and later that week received a response saying my request has been completed and the bank details successfully changed. To my surprise only 1 of the account payments went off the new and correct bank account, the other 3 account payments went off the incorrect old bank account, which then went into overdraft (which in turn costs me more now on overdraft fees and bank charges). My argument now is who is going to pay those bank charges incurred? When I contact Wesbank now again to ask what is going on the woman told me that I need to submit 1 form for each account number separately? Why was I not told this in the first place and also when I then submitted the form (incorrectly apparently) with all the account numbers on 1 form why did they not respond and inform me that they were only changing the 1?