ADT- accounts department not issuing credit note or statement

I have installed a new alarm at my house and wrong advise have been given by their consultant. The outside Beam had to be removed and now it has been more than a month just to get a credit note and statement from them. Numerous messages and emails have been sent. Even after all my emails, their accounts department will phone me for the outstanding amount even when they know about the credit note. On their website it states that a credit note takes a week, why am I then waiting more than a month.