Open account on Credit Report

We closed our Telus mobility account in 2021 upon moving to Europe for a few years. We missed the final balance payment in the busy-ness of moving and the case was referred to a collection agency, and we promptly paid the outstanding balance of $80. 
We have been back in Canada since 2023 and are once again Telus customers (new account number as they couldn’t reopen the closed account). However, after more than five years, there is still an “Open account” status for Telus on my Credit Report with the missed payment and my credit score has taken a real hit because of it. 

I contacted Telus customer service who claim they can’t help me because it’s an old account. The collection agency was nice enough to provide me with a letter confirming the payment back in 2021 and said Telus is responsible for closing this account. I don’t know who to contact anymore!