Reputations are built after a stream of first impressions converge and people start communicating and comparing notes about their experiences then reveling in the common ground whether it be positive or negative. Its just human nature and an important survival skill.
It takes consistent change of behavior for an extended duration of time to change a bad reputation. It also takes willingness on the part of the one who made the judgment to let go of their ego and be open to changing their mind. No easy task to change a reputation to be sure.
Priority #1: Take on a marketing campaign emphasizing the change. Be earnest in admitting an understanding about why things needed to change and the resulting empowerment and enthusiasm since making the change.
Priority #2: Strive to make every future first impression positive to the extent possible. Release the anxiety when finding those who refuse to allow a reputation to change or who form a negative first impression due to reasons you can’t control.