*****ulent-Over charging

I took a contact with this company and just recently changed banks, I emailed them to update my banking details for the debit order to move to new account, the company goes ahead update ,I even receive a notification to approve the debit order and it was successfully but comes the end of the month they charge both of my bank accounts the old one and new the account and when I call the company no one seems to be able to provide me with answers and refund me my money back . This company is *****ulent