You need to contact the credit reporting company that placed the negative information about your father on his credit report and explain what you did and that it was not proper. Your father needs to do the same thing and provide documentation that the signature of your father on the student loan is not his signature ans was done improperly and without his knowledge or later consent.If the credit reporting agentcy will not take the negative mark on your father's credit report off, then he might consider hiring a credit repair company to help him out.You should pay out of your own money the cost of the credit repair company for your father.