Changing banking details

I have requested banking details to be changed in October. To date, details have not been changed. They are full of excuses, first it was done. Then they never received the banking details. Then the accounts is slow. December it is done again. No debit went off. Then its my fault because I put of reversal on the debit order but ADT actually credited the wrong account and denying that they did so. She blamed me but I knew she was lying cause I did a reversal on the incorrect account debited. All I want you simple banking details to be changed. Not even the \ manager"can help or correct this. Because of this I am now in arrears. """