Payment error

I updated my banking details for debit order payment on the self service website. I received a letter confirming the updated payment details. There was one debit order which was unauthorised becaused I had already paid cash by then. But after that on my profile the next debit order is due 27/10/2020 and of which I dont know why. But apparrently from the call I received, I am still supposed to do cash payments and I missed an instalment. Please rectify this as your staff is unwilling to assist.