Bad service on updating my account

Bad service I got from the sales department they are not clearing the arrears whereas I am not owing them I paid even though on my bank statement it shows that it has deducted on December but they said I did not pay. One of the agent today I called she said my account is cleared when it is not I then called another one who told me that my account is still in arrears as a paying customer your delay and making my clear score very bad...