How many times does it take for you to get is right?

Over the last year, I have been trying to get Experian to update my profile and clear the account that has been paid up. I have sent them the paid-up letters and received 2 emails stating that it has been resolved but it still appears on my account. I have tried calling them and spending more than 30mins at a time without any joy. This is now affecting my ability to apply for a home load and stopping me from moving forward in my life. All I ask is for them to update and removed invalid account so my credit score can improve.