public void ApplyPaymentCharge(string pawnID)
{
DataManager dataManager = new DataManager(connectionString);
double financeChargePercent = Convert.ToDouble(GetFinanceCharge());
double newBalance;
double financeCharge;
double principalAmount = dataManager.GetMaxPaymentPrincipal(pawnID);
financeCharge = principalAmount * financeChargePercent;
newBalance = principalAmount + financeCharge;
dataManager.UpdatePawnChargesTable(pawnID, DateTime.Today, financeCharge.ToString(),
principalAmount.ToString(), newBalance.ToString());
}