The US Justice Department said Thursday it has filed a complaint against US business software giant Oracle accusing it of overcharging on a government software contract.The suit alleges that Oracle Corp. and Oracle America Inc. defrauded the United States on a software contract with the General Services Administration (GSA) that involved hundreds of millions of dollars in sales."The contract required Oracle to update GSA when commercial discounts improved and extend the same improved discounts to government customers," the Justice Department said in a statement.