after Debit order has been changed and confirmed they still debit from wrong acount

I am upset not only with my previous not sorted yet and being ignored on that.

i called the call center to changed my debit order and was told i must go in to a store witch i took a day off for and witch i did 2 weeks before my debit order, FNB confirmed it has been changed,

OH! guess what ? you debit order the wrong account witch went in to a over draft, now i have to take a day off again to go in to the banks to sort out MTN's mistakes, after i received a confirmation sms that my debit or was changed it was not. i wanted to close the old account witch i cant because MTN decided to ignore the changes and still take money form a account that was removed from their system and replaced with a old one. Please fix this ASAP.