Currency should be default value irrespective of the previous expense report currency

By default, Currency of the expense report for US employees is USD and for UK employees, it is GBP. If an employees creates an expense with currency other than USD, then this currency is getting stored. When this employee is creating a new expense again, the currency is getting defaulted to previous report currency. The requirement is that the currency should always be USD or GBP regardless of the previous report being in non USD.

Is this the current system functionality or is there a way to achieve this?