public virtual List <tbt_MonthlyBillingHistory> GetLastBillingHistory(string contractCode, string billingOCC, string c_CURRENCY_LOCAL, string c_CURRENCY_US)
        {
            BLDataEntities context = new BLDataEntities();

            return(context.GetLastBillingHistory(contractCode, billingOCC, c_CURRENCY_LOCAL, c_CURRENCY_US).ToList());
        }