Using EPPlus -export to excel, set range as Text to a specific column

am using EPPlus to export data to excel(from MemoryStream), below is the code

private static MemoryStream ExportToExcelAsStram(DataSet ds)
{
    MemoryStream ms = new MemoryStream();
    ExcelPackage package = new ExcelPackage(ms);
    try
    {
        for (int i = 0; i < ds.Tables.Count; i++)
        {

            ExcelWorksheet worksheet = package.Workbook.Worksheets.Add((ds.Tables[i].Rows[i]["Date"]).ToString());

            using (ExcelRange rng = worksheet.Cells["B1 : B" + (ds.Tables[i].Rows.Count + 1)])
            {
                rng.Style.Numberformat.Format = "#";
            }

            //worksheet.Cells["B1 : B" + (ds.Tables[i].Rows.Count + 1)].Style.Numberformat.Format = "@";
            worksheet.Cells["A1"].LoadFromDataTable(ds.Tables[i], true);

            //Format the header for column 1-9
            using (ExcelRange range = worksheet.Cells[1, 1, 1, 12])
            {
                range.Style.Font.Bold = true;
                range.Style.Fill.PatternType = OfficeOpenXml.Style.ExcelFillStyle.Solid;
                range.Style.Fill.BackgroundColor.SetColor(System.Drawing.Color.DarkRed);
                range.Style.Font.Color.SetColor(System.Drawing.Color.White);
            }

            worksheet.Cells["A1:L" + (ds.Tables[i].Rows.Count + 1)].Style.Border.BorderAround(OfficeOpenXml.Style.ExcelBorderStyle.Thin, System.Drawing.Color.Black);
            worksheet.Cells["A1:L" + (ds.Tables[i].Rows.Count + 1)].Style.VerticalAlignment = ExcelVerticalAlignment.Center;
            worksheet.Cells["A1:L" + (ds.Tables[i].Rows.Count + 1)].Style.HorizontalAlignment = ExcelHorizontalAlignment.Center;

        }

    }
    catch (Exception ex)
    {
        throw ex;
    }
    package.Save();
    ms.Position = 0;
    return ms;
}

i need to set the format of column B as text. i gave the range specifically for column B, but once the excel is generated this formatting is applied for all other columns. Please help me solve this... thanks in advance.