Verrry Bad service from FNB Personal loans

I have a personal loan account with FNB personal loans, and they have been debiting from my FNB account. I called the call centre in February 2023 to change my bank account details as I no longer bank with FNB and I was told that FNB does not debit from my new bank Discovery bank, which was absurd, till today everytime i call to amend my details, they drop my calls. this is very unacceptable, as i have to keep an account that i no longer need just to have FNB personal loans debit going off from it.