Client not satisfied with double deduction

Discovery deducted two premiums from my bank account which was on 2nd and 3rd February 2021. This is after i phoned them to inform them that the debit order didn't go off as discussed on the 1st of February 2021. These people were so quick to join me up, but now to sort outthis double deduction is as difficult as a mission to mars. I dont get through to the accounts department.