Useless call center staff & managers

Since December i have requested that my banking details be changed on my wife and my accounts yet every time they manage to stuff it up on one of the accounts then revert back to the old account . I don't know if the call centre is just incapable of working or they just don't want to. Even if you ask for a manager to do it they say its done and will call back in 48 hours to see if the debit went off the new account yet low and behold i am still waiting for the call back from the previous 2 managers and banking details are still incorrect. Probably the worst service i have gotten in South Africa and we all know how bad that is. I will be sure to tell everyone how bad your company is in the future.