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I guess I am at fault, however, the fact that they had taken my bank details, taken the outstanding amount and 'confirmed' that my DD was set up (and even had the complaint team staff member admit this was their error) to me shows that it was in no part my error. I gave all the details as they asked and in good faith gave them the details. If they didn't use those details correctly, that is an internal issue.
I'll have to wait for them to get in touch.