Service pathetic

Went to their branch at Horizon View for assistance on changing bank details on my funeral policy. Was told that they cannot assist me. I have tried to change bank details on App to my current bank details but cannot change bank details. Costs are going to be occured on my side as the number is charged fee. How can a bank not have the facility to change bank details as failed debit order will charge me on old account and can make my policy to suspend