Banking Details has still not been changed

I spoke to 5 people at Vodacom over the phone to change my banking details and still its not changed ,I phoned from the 17th of September 2015 to correct it and still its not changed. Every time i ask them if it has been changed they tell me yes and when i phone them again then their was nothing done!! I'm getting a bad name because my debit order are getting send back because they don't change my banking details