how to fix my gridview from doubling the columns

I have a gridview with template items and am binding the gridview with a data table. What is happening is that the columns with the textboxes, etc are populating, but then extra columns from the data table with the same data is being added to the end of the gridview. code is attached. I tried to clear the gridview, but it got rid of the template item fields.

aspx.cs

protected void Page_Load(object sender, EventArgs e)
        {
            //forces postback when the treeview iten's check box is clicked.
            tvContracts.Attributes.Add("onclick", "postBackByObject()");

            ManagedUser = (Administrator)HttpContext.Current.Session["UserObject"];

            //Populating all drop downs for the contract modal window.
            if(!IsPostBack)
            {
CallOptions.fillEmptyCallOptionGV(CallOptionGV);
            }
        }


calloption.cs

public void fillEmptyCallOptionGV(GridView GV)
        {
            dt = new DataTable();

            dt.Columns.Add("NAME");
            dt.Columns.Add("CALL_OPTION_NAME");
            dt.Columns.Add("COUNTERPARTY_NOTIFICATIONS");
            dt.Columns.Add("EMO_NOTIFICATIONS");
            dt.Columns.Add("COUNTERPARTY_EMAILS");
            dt.Columns.Add("EMO_EMAILS");
            dt.Columns.Add("TRADES_DEAL_NUMBER");
            dt.Columns.Add("DEFAULT_TO_AVAILABLE");
            dt.Columns.Add("POR_AVAILABILITY");
            dt.Columns.Add("MW");
            dt.Columns.Add("ALLOW_ADDITIONAL_MW");
            dt.Columns.Add("SELLER_AVAILABILITY_BY");
            dt.Columns.Add("EMO_STRIKE_NOTICE_BY");
            dt.Columns.Add("MIN_RUN_TIME");
            dt.Columns.Add("MIN_DOWN_TIME");
            dt.Columns.Add("STARTS_PER_DAY");
            dt.Columns.Add("EMO_INTRADAY_CHANGES_BY");
            dt.Columns.Add("MIN_CONTRACT_STARTS");
            dt.Columns.Add("MAX_CONTRACT_STARTS");
            dt.Columns.Add("ADDITIONAL_START_CHARGE");
            dt.Columns.Add("COMMENTS");
            dt.Columns.Add("ID");

            dt.Rows.Add(new object[] { "A", "", "0", "0", "", "", "", "1", "", "", "", "", "", "", "", "", "", "", "", "", "", "1" });
            dt.Rows.Add(new object[] { "B", "", "0", "0", "", "", "", "1", "", "", "", "", "", "", "", "", "", "", "", "", "", "2" });
            dt.Rows.Add(new object[] { "C", "", "0", "0", "", "", "", "1", "", "", "", "", "", "", "", "", "", "", "", "", "", "3" });

            GV.DataSource = dt;
            GV.DataBind();

        }

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<asp:GridView ID="CallOptionGV" runat="server" BackColor="White" Width="1200" OnRowDataBinding="CallOptionGV_RowDataBound" DataKeyNames="ID" 
        BorderColor="#DEDFDE" BorderStyle="None" BorderWidth="1px" CellPadding="4" Font-Size="Small"
        ForeColor="Black" GridLines="Vertical">
            <AlternatingRowStyle BackColor="White" />
            <Columns>
                <asp:BoundField DataField="id" HeaderText="id" Visible="false" InsertVisible="False" ReadOnly="True"
SortExpression="id" />
                <asp:TemplateField HeaderText="Product Name" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtProductName" runat="server" Width="20" MaxLength="1" Text='<%# Bind("NAME") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Call Option Name" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtCallOptionName" runat="server" Width="75" Text='<%# Bind("CALL_OPTION_NAME") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Counterparty Notifications" InsertVisible="true">
                    <ItemTemplate>
                        <asp:RadioButtonList ID="RdCounterNotification" runat="server">
                            <asp:ListItem Text="Yes" Value="0"></asp:ListItem>
                            <asp:ListItem Text="No" Value="1"></asp:ListItem>
                        </asp:RadioButtonList>
                    </ItemTemplate>
                </asp:TemplateField> 
                <asp:TemplateField HeaderText="EMO Notifications" InsertVisible="true">
                    <ItemTemplate>
                        <asp:RadioButtonList ID="RdEMONotification" runat="server">
                            <asp:ListItem Text="Yes" Value="0"></asp:ListItem>
                            <asp:ListItem Text="No" Value="1"></asp:ListItem>
                        </asp:RadioButtonList>
                    </ItemTemplate>
                </asp:TemplateField> 
                <asp:TemplateField HeaderText="Counterparty Email Groups" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtCounterEmail" runat="server" Width="100" Text='<%# Bind("COUNTERPARTY_EMAILS") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="EMO Email Groups" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtEMOEmail" runat="server" Width="100" Text='<%# Bind("EMO_EMAILS") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Trades Deal Number" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtTradesNo" runat="server" Width="70" Text='<%# Bind("TRADES_DEAL_NUMBER") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Availability Default to Option Volume" InsertVisible="true">
                    <ItemTemplate>
                        <asp:RadioButtonList ID="RdDftOptionVol" runat="server">
                            <asp:ListItem>Yes</asp:ListItem>
                            <asp:ListItem>No</asp:ListItem>
                        </asp:RadioButtonList>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="MW" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtMW" runat="server" Width="50" Text='<%# Bind("MW") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField> 
                <asp:TemplateField HeaderText="Allow Additional MW" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtAddMW" runat="server" Width="50" Text='<%# Bind("ALLOW_ADDITIONAL_MW") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField> 
                <asp:TemplateField HeaderText="Seller to Provide Availability by" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtSellerBy" runat="server" Width="50" Text='<%# Bind("SELLER_AVAILABILITY_BY") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="EMO to Provide Schedule/Strike Notice by" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtEMOBy" runat="server" Width="50" Text='<%# Bind("EMO_STRIKE_NOTICE_BY") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Minimum Run Time" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtMinRunTime" runat="server" Width="50" Text='<%# Bind("MIN_RUN_TIME") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField> 
                <asp:TemplateField HeaderText="Minimum Down Time" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtMinDwnTime" runat="server" Width="50" Text='<%# Bind("MIN_DOWN_TIME") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Starts Per Day" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtStartsPerDay" runat="server" Width="30" Text='<%# Bind("STARTS_PER_DAY") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="EMO to Provide Intraday Changes by" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtEMOIntraChg" runat="server" Width="50" Text='<%# Bind("EMO_INTRADAY_CHANGES_BY") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Minimum Starts During Contract Term" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtMinStarts" runat="server" Width="30" Text='<%# Bind("MIN_CONTRACT_STARTS") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Maximum Starts During Contract Term" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtMaxStarts" runat="server" Width="30" Text='<%# Bind("MAX_CONTRACT_STARTS") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Additional Start Charge for Dispatch > 24 Hours" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtStartCharge" runat="server" Width="80" Text='<%# Bind("ADDITIONAL_START_CHARGE") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Comments" InsertVisible="true">
                    <ItemTemplate>
                        <asp:TextBox ID="txtCallOptionComments" runat="server" Width="100" Text='<%# Bind("COMMENTS") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>    
            </Columns>
            <FooterStyle BackColor="#CCCC99" />
            <HeaderStyle BackColor="#6B696B" Font-Bold="True" ForeColor="White" />
            <PagerStyle BackColor="#F7F7DE" ForeColor="Black" HorizontalAlign="Right" />
            <RowStyle BackColor="#F7F7DE" />
            <SelectedRowStyle BackColor="#CE5D5A" Font-Bold="True" ForeColor="White" />
            <SortedAscendingCellStyle BackColor="#FBFBF2" />
            <SortedAscendingHeaderStyle BackColor="#848384" />
            <SortedDescendingCellStyle BackColor="#EAEAD3" />
            <SortedDescendingHeaderStyle BackColor="#575357" />
        </asp:GridView>

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