Where a defendant was not aware that the plaintiff was being charged fees due to its use of Fannie Mae computer system, claim for unjust enrichment failed.The 7th U.S. Circuit Court of Appeals affirmed a decision by U.S. District Judge Lynn Adelman, Eastern District of Wisconsin.Nationwide Advantage Mortgage Co. of Des Moines, Iowa, a subsidiary of Nationwide Mutual Insurance Co., buys, services and sells residential mortgages. GSF Mortgage Corp. is a residential mortgage lender that also sells mortgages with its …