The fastest way to delete inaccurte information is to have a lender get involved in the file. Lenders have options to perform what is referred to as a "Rapid Rescore". There is a cost to make the corrections, fees charged by each credit repository.
If the lender your client is working with is unable to assist that would be an odd thing.
If the inaccurate information is the result of IDENTITY THEFT, then that is a horse of a different series of agonizing events. If that is the case there is an amazing series of resources available to assist the individual who has been affected, none of it is quick. View the government's public service announcement regarding identity theft at http://katinawright.point2agent.com . The video provides additional online resources available to help address the issue.