Have you been bankrupt? If so then you need to send a copy of your discharge to the data controller at the creditor concerned and tell them to put the default date back to date of bankruptcy.
If it's an IVA then you do the same but with your completion letter.
A DMP will stay as a default until the debt is paid off.
Follow through Make your dreams come true Don't give up the fight You will be alright 'Cause there's no one like you in the universe