Refuse paid up letter

Ive made my last payment on 1st December after I've realised my credit profile has not been updated for months. After its supposed to be updated by the 9th of each month. Its almost the 9th of February, 3months later. Asking me to be patient by consultant. I requested the paid up letter and currently struggling to get the correct letter with the correct account number. How can a company refuse to change the number as i do have the statement with the same number but cant be added to the paid up letter. Please explain this *********** service?? I need the correct paid up letter to qualify for a new car! Its really annoyed to deal with this *********** people who cant help as you owe them no money! Its a simple request to provide me with the correct paid up letter! All my airtime to explain if for probably the 10th person in a row!