ASP.net web method, rewrite URL

Question

I have written a ASP.net web method in C# that takes a Parameter Customer reference before displaying the customer balance. It can be accessed via http://localhost:59294/api/Balance/getAccountBalance.aspx?CustomerReference=tk20000

The application consuming it wants the URL as http://localhost:59294/api/Balance/getAccountBalance(tk20000). How do I go about URL rewrite? Kindly assist.

[WebMethod]

public void getAccountBalance(string CustomerReference)
{
    List<Customer> listEmployees = new List<Customer>();
    OdbcDataReader rdr;
    string cs = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (OdbcConnection con = new OdbcConnection(cs))
    {
        OdbcCommand cmd = new OdbcCommand();
        cmd.Connection = con;
        cmd.CommandType = System.Data.CommandType.Text;
        string querystring = "SELECT TOP 10 " + qt + "CardCode" + qt + ", " + qt + "Balance" + qt + ", " + qt + "Currency" + qt + "  FROM " + qt + "TSLHANA" + qt + "." + qt + "OCRD" + qt + "WHERE " + qt + "CardCode" + qt + "= '" + CustomerReference + "'";
        cmd.CommandText = querystring;

        if (con.State != ConnectionState.Open)
        {
            con.Close();
            con.Open();
            cmd.Connection = con;
            rdr = cmd.ExecuteReader();
            while (rdr.Read())
            {
                Customer customer = new Customer();
                //customer.CardCode = rdr["CardCode"].ToString();
                // customer.LoyaltyCustomerReference = rdr["U_LoyaltyCustomerReference"].ToString();
                customer.Balance = rdr["Balance"].ToString();
                // customer.Currency = rdr["Currency"].ToString();
                listEmployees.Add(customer);
            }
            con.Close();
            con.Dispose();
        }
    }
    if (listEmployees.Count >= 1)
    {
        JavaScriptSerializer js = new JavaScriptSerializer();
        Context.Response.Write(js.Serialize(listEmployees));
    }
    else
    {
        string dqt = "\"";
        Context.Response.Write("[{" + dqt + "Error" + dqt + ":" + dqt + "No records found for customer " + CustomerReference + dqt + "}]");
    }
}