Credit information inaccuracy

I had a loan which I paid off on the 23rd of March 2018. I requested the paid up letter in June 2018 and sent it to Transunion to update my credit information. To my surprise I noticed the amount still shows up on my debt analysis on Friday the 05th of July 2019, so I called Transunion to dispute this information. I asked the agent to forward the letter and he said it was not necessary. This morning (11 July 2019), I receive a notification that my query has been closed and they found sufficient evidence in support of the credit provider, how when I have a letter confirming that the account was paid up in full? Where can I send this proof because I want this issue resolved. All the email addresses are no longer in use and clearly speaking to agents doesn't help!