Account 30 days arrears when i've settled it!!!!!!

I settled my account in full and received a zero balance letter from them, now they say I have a balance of R503 on my account, which account? They updated my status on Transunion with a 120 days arrears a few months ago which was incorrect and now 30 days arrears after receiving a paid up letter and after they updated my status on Transunion as Cancelled. This is my life, my credit record that's being jeopardized by *********** sales people/accountants!!!