Experian failing to rectify mistake on my credit report

I wonder why does it takes for ever for experian to rectify mistakes on credit report, I had payed both my avon and rage account and told me that rage said my account it's unpaid but when I call rage they said they sent the correct statement to experian that I paid but my credit report remained unchanged... I'm really tired of experian with how they conduct their work its been 2months now