Not possible for Nedbank to change notification cell number.

It is now 6 months since I requested Nedbank to change my notification cell phone number for my 3 accounts. They managed to change it for my check account but not for my garage card and credit card. After several attemps (according to them) the notifications still come through to the wrong number. Not sure if the IT department was informed of this problem or if they are ***********. Hoe difficult can it be?