Un authorized debit order.

Last year December Best electric actioned a debit order long before the agreed December date. I contacted them and requested to reverse the debit order as I still needed money that was in my bank account. They said"they could not reverse". Naturally I was up set and told them how I felt about it. I also asked them to correct the December deduction date. Low and behold.. They did it again today. My date for debit orders are set for the 30th of December and today the 11th December they debit my account. I still need my money for petrol. Food etc. They still are doing what they want and does not respect my wishes as a customer. P