Problem trying to empty and load a DataGridView in C#

I am trying to load a DataGridView with a list of filtered partners, but at the time of loading I load all the partners plus those that I filter. I don't see where the error could be. The filter is applied while you write, to explain myself better: if I enter fra it has to show all the members, whose names start with those 3 letters, such as Franco, Francisco, Franca, etc.

The textBox code is as follows:

private void txt_filtro_nombre_TextChanged(object sender, EventArgs e)
        {       
            if (!String.IsNullOrWhiteSpace(txt_filtro_nombre.Text))
            {
                cargarGrilla(svSocio.getSocioPorNombre(txt_filtro_nombre.Text));
            }
        }

The code getSocioPorNombre(textbox)that brings me the data is as follows:

public IList<DTO_Socio> getSocioPorNombre(string nombre)
        {
            IList<DTO_Socio> lista = new List<DTO_Socio>();
            IList<Socio> listaSocios = dao.getSociosPorNombre(nombre);
            foreach (Socio socio in listaSocios)
            {
                lista.Add(mapSocio.getDtoSocio(socio));
            }

            return lista;
        }

which communicates with the DAO that brings me the data from the database and has this code:

public IList<Socio> getSociosPorNombre(string nombre)
        {
            string sp = "listar_socios_por_nombre";
            var parametro = new SqlParameter("@nombre", nombre);
            parametro.SqlDbType = SqlDbType.VarChar;

            IList<Socio> listaSocios = getSocios();
            DataTable tabla = helper.consultarStoredProcedureConUnParametro(sp, parametro);
            foreach (DataRow fila in tabla.Rows)
            {
                listaSocios.Add(mapper(fila));
            }
            return listaSocios;
        }

The helper code that communicates with the database:

public DataTable consultarStoredProcedureConUnParametro(string sp, SqlParameter parametro)
        {
            SqlConnection cnn = new SqlConnection();
            SqlCommand cmd = new SqlCommand();
            DataTable tabla = new DataTable();

            try
            {
                cnn.ConnectionString = string_conexion;
                cnn.Open();
                cmd.Connection = cnn;
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.CommandText = sp;
                cmd.Parameters.Add(parametro);
                tabla.Load(cmd.ExecuteReader());
                return tabla;
            }
            catch (SqlException ex)
            {
                MessageBox.Show("EXPLOTO EL HELPER", "ERROR", MessageBoxButtons.OK, MessageBoxIcon.Error);
                throw (ex);
            }
            finally
            {
                this.CloseConnection(cnn);
            }
        }

The code ofcargarGrilla():

dgv_socios.Rows.Clear();
            if (lista != null)
            {
                foreach (DTO_Socio dto in lista)
                {
                    dgv_socios.Rows.Add(new Object[]
                            {
                                dto.NumeroSocio,
                                dto.Nombre,
                                dto.Apellido,
                                dto.Dni
                            }
                        );
                }
            }
            else
            {
                MessageBox.Show("No hay datos para mostrar", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }

I can't see where the error is, for which it brings me all the partners + the filtered ones.

I leave you an image of what I say

Run the SP on the database to see if that failed, but it works great