problems when inserting new data to excel using datatables

I do not know how to explain my problem very well. I have never known how to do it with certainty.

I will start by showing you my code where I ask the user to enter the following information: Name, last name, age and sex. These data will be saved in Excel. Keep in mind that the file already has data stored in it.

my code is as follows:

void EscribirEnExcel(string pathfile)
 {

    string nombre="", apellido = "", sexo = "";
    char opt;
    int? Edad = null;
    SLDocument sL = new SLDocument(pathfile);
    SLWorksheetStatistics stats = sL.GetWorksheetStatistics();
    System.Data.DataTable dataTable = new System.Data.DataTable();
    int row = stats.EndRowIndex;
    Console.WriteLine(row);

    do {
        Console.WriteLine("Desea añadir más datos? Si(y) No(n) ");
        opt = Convert.ToChar(Console.ReadLine());
        row++;
        switch (opt)
        {
            case 'y':

                Console.WriteLine("Escriba su: nombre,apellido,edad y sexo");
            nombre = Console.ReadLine();
            apellido = Console.ReadLine();
            Edad = Convert.ToInt32(Console.ReadLine());
            sexo = Console.ReadLine();

            dataTable.Columns.Add("Nombre", typeof(string));
            dataTable.Columns.Add("Apellido", typeof(string));
            dataTable.Columns.Add("Edad", typeof(int));
            dataTable.Columns.Add("Sexo", typeof(string));

                //registros
                dataTable.Rows.Add(nombre, apellido, Edad, sexo);
            sL.ImportDataTable(row, 1, dataTable, false);
                sL.Save();

            break;

            case 'n':
                break;

        }
    } while (opt != 'n') ;

 }

The second time I try to enter data into the file it shows me the following error: 'The column' Name 'already belongs to DataTable.' in this part of the code

  dataTable.Columns.Add("Nombre", typeof(string));

And if I remove the columns, the following error appears: 'The input matrix is longer than the number of columns in this table.' in

dataTable.Rows.Add(nombre, apellido, Edad, sexo);

How could I do it in such a way that I can enter the data without being marked by any of the errors mentioned?