Need WHMCS Currency Convert Addon

Hello, We are using WHMCS v 7.10.x We have 3 currencies on our system. TRY ( main currency) , USD and EUR. We want to change our customers currencies to USD from TRY (main currency). The problem is; when we change currencies, all active invoices changes also. We need to change our customers currencies to USD but remains old currency for active invoices. We are waiting your offers about this.