Liberty entered incorrect banking details update.

I contacted liberty two months ago to change my banking details. My new bank also contacted them regarding debit order switching. They have confirmed to have done so. I received two notices of unpaid debits despite early notification and adequate funds in my account. I have sent numerous emails to them with promising replies to update my account details. When I logged in online to view my accounts I discovered that liberty incorrectly updated my account details. Somebody has obviously not been doing their work right and now I am being harassed by emails of unpaid policies!!!! I had to correct these changed myself. I am appalled by this service and I request an apology by Liberty.