Difficult to change debit order details. Poor communication

I am trying to change my debit order details. Which seem impossible. I went to a shop and they said I must call. Then I logged in online and there are no options for changing payment details. Then I phoned and after a ling time of entering ID nr and Card number and waiting I cane through to an agent.with a lot of voices and noise in the background.

I explained to the agent that I need to change my debit order. She apparently didn't hear what I was saying (considering all the loud talking in the background Incan understand). I explained again. The the call was dropped.

I finished my air time. And can't call back again.

Should my debit order fail, this is a notice that I did try to update my new bank details.