Can't get hold of the right department -no one can "help"

I am still waiting for the paid up letter that has been requested after a cancelled contract was incorrectly billed. After almost a year of struggling - I was assured I would get the letter within 10 days - it is now almost a month later!!! Part of the problem has been resolved, but this is a big problem and needs urgent resolution please We need to complete a home loan bond approval and this letter is holding everything up - PLEASE PLEASE PLEASE can I have the paid up letter urgently!!