Not doing what is asked

We stopped a debit order by the last month and it went off this month again!we went to ask them to reverse it on Tuesday 2 June and they said it would be in our acc in 24 hours but it wasnt and thursday we phoned and they said they have to first send a lettle of premission to ask if they can reverse it! We have other things to pay but cant because they are not doing as they are asked!