Procedure Or Function Has Too Many Argument Specified.

 Hey, friends, i have a problem on my bank transaction page now: Procedure or function has too many argument specified.
people can log in by their usernames, 1 username can have many accounts, there are 2 account types:'c', 's'.
after people login, they are only allowed to withdraw money from their own account: here is some of my codes: 
 1 else if (DropDownList3.SelectedItem.Text == "withdraw")
2 {
3 SqlConnection sqlCon = new SqlConnection("Data Source=bandicoot.cs.rmit.edu.au;Initial Catalog=shuli;User ID=test;Password=test");
4 SqlCommand cmd = new SqlCommand("usp_withdraw", sqlCon);
5 string spResult = "";
6 cmd.CommandType = CommandType.StoredProcedure;
7 cmd.Parameters.Add("@username", SqlDbType.NVarChar).Value = Session["username"].ToString();
8 cmd.Parameters.Add("@AccountFrom", SqlDbType.VarChar).Value = TextBox3.Text;
9 cmd.Parameters.Add("@Amount", SqlDbType.Decimal).Value = TextBox5.Text;
10 cmd.CommandType = CommandType.StoredProcedure;
11 sqlCon.Open();
12 spResult = cmd.ExecuteScalar().ToString();
13 if (string.Compare(spResult, "Execute successfully") == 0)
14 {
15 SqlDataSource with = new SqlDataSource();
16 with.ConnectionString = ConfigurationManager.ConnectionStrings["shuliConnectionString"].ToString();
17
18 with.InsertCommand = "insert into Transactions(TransactionType,AccountNumber,DestAccount,Amount,Comment,ModifyDate) values ('W','" + TextBox3.Text + "','" + TextBox3.Text + "','" + TextBox5.Text + "','" + TextBox2.Text + "','" + DateTime.Now.ToLocalTime() + "')";
19 int inertRowNum = with.Insert();
20 Server.Transfer("~/deposit_withdraw_confirm.aspx");
21 }
22 else
23 {
24 Server.Transfer("~/deposit_withdraw_error.aspx");
25 }
26
  here is my store procedure

 set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go




-- =============================================
-- Author:        <Author,,Name>
-- Create date: <Create Date,,>
-- Description:    <Description,,>
-- =============================================
ALTER Procedure [dbo].[usp_withdraw]
(
    @AccountFrom Varchar(20),
    @Amount Decimal(10,2)
)
As
DECLARE @ReturnMsg AS VARCHAR(20)
DECLARE @balance AS Decimal(10,2)
DECLARE @username AS nvarchar(50)

SELECT @balance = balance
FROM Account,Login
WHERE   Account.CustomerID=Login.CustomerID AND Login.UserID= @username and
AccountNumber = @AccountFrom

IF (
    SELECT AccountType
    FROM Account, Login
    Where  Account.CustomerID=Login.CustomerID AND Login.UserID= @username and AccountNumber = @AccountFrom
    ) ='c'
BEGIN
     BEGIN TRAN
        IF (@balance - @Amount) > 199                            
        BEGIN
            UPDATE Account
            SET balance= balance-@Amount
            WHERE AccountNumber=@AccountFrom
                  And (balance - @Amount) > 199                                

            SET @ReturnMsg = 'Execute successfully'
            COMMIT TRAN
        END
        ELSE
        BEGIN
            SET @ReturnMsg = 'Execute with error'
            ROLLBACK TRAN          
        END



    SELECT @ReturnMsg     
END

IF (
    SELECT AccountType
    FROM Account
    Where AccountNumber = @AccountFrom
    ) ='s'
BEGIN
     BEGIN TRAN
        IF (@balance - @Amount) > 0                            
        BEGIN
            UPDATE Account
            SET balance= balance-@Amount
            WHERE AccountNumber=@AccountFrom
                  And (balance - @Amount) > 0                                

            SET @ReturnMsg = 'Execute successfully'
            COMMIT TRAN
        END
        ELSE
        BEGIN
            SET @ReturnMsg = 'Execute with error'
            ROLLBACK TRAN          
        END



    SELECT @ReturnMsg     
END


I think the problem is in Line 7
cmd.Parameters.Add("@username", SqlDbType.VarChar).Value = Session["username"].ToString();this is to get the current login user's uername.