Terrible service

I cancelled my Fixed Line account in September 2017. In December 2018 I was given a bad payment record at TransUnion because of an amount that is still outstanding. I opted to pay the account in full to just get it all done. Today I requested a paid-in full letter to submit my homeloan application and to use it to clear my record with TransUnion. Iam told by the agent that it will take 7 days to respond to my request. 7 days!? I will have to cancel my home-loan application - all because of an error that is not my problem! I need to have this sorted today! I was told that a manager would call me back, but nobody has called me!