unauthorised debit order

I settled my account with RCS ,however a debit order was still processed ,and when I contacted the accounts regarding the refund I was told it would be done ,but every time I phoned to confirm if the payment was processed ,I kept getting the same response, that they needed a bank statement ,and I sent the statement immediately to them weeks ago ,and then they would respond saying it would be the next week or the week after. I feel they are very unfair and that it was they fault in the first place and there is no excuses ,we trusted RCS and gave our bank details ,how many other people are being affected.