Mistaken Identity and Credit Rating

[Noodles]

Background:

A little over two years ago, we received a mail from a collection agency asking my wife to pay a hospital bill. Needless to say, this was a mistake. The person who incurred the bill had the same first name and last name as my wife*. Different second name altogether.

We've called them to make the correction. Sent them whatever documents they require of us to no avail. They've promised to work on it but the record still shows up.

My wife's credit suffered because of this. This is the same women who pays her credit card in full, the day after the bill closes.

What else can we do to rectify this?

*Women from countries influenced by Spain normally has two names e.g. Maria Carmela Esperanza. Maria is rarely used. Usually second and last name.