Account not updated on TransUnion (Credit report)

I had an account with Markham which I settled in 2013. When I checked my credit report, I noticed that they haven't been updating their records. Their record on TransUnion shows as if I still owe them R78.00 which I don't know where it comes from. I then went to Markham retail outlet in Claremont and in Zevenwacht to find out what the R78.00 is for and I was informed that they are not sure, but my account balance on their system shows R0.00. It has been more than two years and I am shocked that the account still reflects negatively under my name. If I was able to settle the account, what would have stopped me from paying that R78.00? I would like Markham to remove that amount and clear my record from 2013 when the account was settled.