Pathetic Service from the Vehicle Finance Division

For the past couple of months, I have been trying to change my banking details where my debit goes off and have been unsuccessful due to the unprofessionalism of standard bank employees. I have sent my documentations in time more than 3 times and every time a few weeks after I have sent my document I will receive an e-mail stating I should have sent my documents in time. I feel like the people responding to my e-mails are not reading the e-mails I am sending because I have explained three times already that I do not want to change my debit date but rather my banking details.