Updating A Database From A Web Service

I have this code in a web service, but when I try to update the database using the second method (setContacts), it does not update at all, although I do not get an error message.
[WebMethod]
public DataSet getContacts()
{
using (SqlConnection con = new SqlConnection(connString))
{
DataSet ds = new DataSet("Contacts");
SqlCommandBuilder cb = new SqlCommandBuilder(da);
da = new SqlDataAdapter("SELECT * FROM Contacts", con);
da.Fill(ds);
return ds;
};
}
[WebMethod]
public void setContacts(DataSet data)
{
using (SqlConnection con = new SqlConnection(connString))
{
DataSet ds = new DataSet("Contacts");
SqlCommandBuilder cb = new SqlCommandBuilder(da);
da = new SqlDataAdapter("SELECT * FROM Contacts", con);
da.Update(data, "Contacts");
};
}

(Updated Code 10:47 PM)

Here is sample Project I have provided with database that i coded for you !! that update database from webservice

just take a look

i called UpdateMethod Like below ..

   protected void btnUpdate_Click(object sender, EventArgs e)
    {
        string Username = TextBox1.Text;
        string newPassword = TextBox2.Text;
 
        localhost.Service1 srv = new localhost.Service1();
 
        // Update the Userpassword By Calling webmethod of service
        srv.UpdateUser(Username, newPassword);
    }