diff --git a/.gitignore b/.gitignore
index 3a9875b..a75dba1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 /vendor/
 composer.lock
+.idea
diff --git a/composer.json b/composer.json
index 72e84c0..391f84d 100644
--- a/composer.json
+++ b/composer.json
@@ -4,7 +4,7 @@
     "require": {
         "ext-json": "*",
         "php": ">=7.1",
-        "symfony/framework-bundle": ">=2.1",
+        "symfony/framework-bundle": "4.4.*",
         "psr/log": "~1.0",
         "phpoffice/phpspreadsheet": "^1.3"
     },
diff --git a/src/Resources/config/services.yml b/src/Resources/config/services.yml
index 246e7af..7a111e0 100644
--- a/src/Resources/config/services.yml
+++ b/src/Resources/config/services.yml
@@ -11,7 +11,7 @@ services:
               - { name: monolog.logger, channel: csvwriter }
 
     excelwriter:
-        class: %excelwriter.service.class%
+        class: "%excelwriter.service.class%"
         arguments: [ "@logger", "@phpexcel" ]
         tags:
               - { name: monolog.logger, channel: excelwriter }
diff --git a/src/Service/ExcelWriter.php b/src/Service/ExcelWriter.php
index 29ba511..61fbd35 100644
--- a/src/Service/ExcelWriter.php
+++ b/src/Service/ExcelWriter.php
@@ -87,10 +87,11 @@ public function setSheetTitle($title)
      *
      * @param $headers
      * @param $initRow
+     * @param $flattenHeaders
      *
      * @throws \PhpOffice\PhpSpreadsheet\Exception
      */
-    public function writeHeaders($headers, $initRow = null)
+    public function writeHeaders($headers, $initRow = null, $flattenHeaders = false)
     {
         $worksheet = $this->spreadsheet->getActiveSheet();
         $hasMultiRowHeaders = $this->hasMultiRowHeaders($headers);
@@ -107,41 +108,56 @@ public function writeHeaders($headers, $initRow = null)
             if (!is_array($header)) {
                 $worksheet->setCellValue($cell, $header);
                 $worksheet->getColumnDimension($column)->setAutoSize(true);
-                if ($hasMultiRowHeaders) {
+                if ($hasMultiRowHeaders && !$flattenHeaders) {
                     // These set of headers contain multi-row headers. So this cell needs to be merged with cell in the
                     // row below it.
                     $worksheet->mergeCells($column . $initRow . ':' . $column . ($initRow + 1));
                 }
+                // Mark headers as bold
+                $worksheet->getStyle($cell)->getFont()->setBold(true);
                 $column++;
             } else {
-                // This is a multi-row header, the first row consists of one value merged across several cells and the
-                // second row contains the "children".
 
-                // Write the first row of the header
                 $arrKeys = array_keys($header);
                 $headerName = reset($arrKeys);
-                $worksheet->setCellValue($cell, $headerName);
-
-                // Figure out how many cells across to merge
-                $mergeLength = count($header[$headerName]) - 1;
-                $mergeDestination = $this->incrementColumn($column, $mergeLength);
-                $worksheet->mergeCells($column . $initRow . ':' . $mergeDestination . $initRow);
-
-                // Now write the children's values onto the second row
-                foreach ($header[$headerName] as $subHeaderName) {
-                    $worksheet->setCellValue($column . ($initRow + 1), $subHeaderName);
-                    $worksheet->getColumnDimension($column)->setAutoSize(true);
-                    $column++;
+
+                if ($flattenHeaders) {
+                    // If $flattenHeaders true, we are going to flatten nested headers as single header row
+                    // We only consider "children" for headers ignoring parent header name completely.
+
+                    // Now write the children's values as flattened header in the row
+                    foreach ($header[$headerName] as $subHeaderName) {
+                        $cell = $column . $initRow;
+                        $worksheet->setCellValue($cell, $subHeaderName);
+                        $worksheet->getColumnDimension($column)->setAutoSize(true);
+                        // Mark child headers as bold
+                        $worksheet->getStyle($cell)->getFont()->setBold(true);
+                        $column++;
+                    }
+                } else {
+                    $worksheet->setCellValue($cell, $headerName);
+
+                    // Figure out how many cells across to merge
+                    $mergeLength = count($header[$headerName]) - 1;
+                    $mergeDestination = $this->incrementColumn($column, $mergeLength);
+                    $worksheet->mergeCells($column . $initRow . ':' . $mergeDestination . $initRow);
+
+                    // Now write the children's values onto the second row
+                    foreach ($header[$headerName] as $subHeaderName) {
+                        $worksheet->setCellValue($column . ($initRow + 1), $subHeaderName);
+                        $worksheet->getColumnDimension($column)->setAutoSize(true);
+                        $column++;
+                    }
+
+                    // Mark parent headers as bold
+                    $worksheet->getStyle($cell)->getFont()->setBold(true);
                 }
             }
-
-            // Mark headers as bold
-            $worksheet->getStyle($cell)->getFont()->setBold(true);
         }
 
         $worksheet->calculateColumnWidths();
 
-        $this->currentRow = $initRow + (($hasMultiRowHeaders) ? 2 : 1);
+        $this->currentRow = $initRow + (($hasMultiRowHeaders && !$flattenHeaders) ? 2 : 1);
     }
 
     /**
@@ -169,13 +185,15 @@ private function hasMultiRowHeaders($headers)
      * @param string $cacheFile Filename where the fetched data can be cached from
      * @param array $sortedHeaders Headers to write sorted in the order you want them
      * @param bool $freezeHeaders True if you want to freeze headers (default: false)
+     * @param bool $flattenHeaders True if you want to flatten nested headers (default: false)
      * @throws \PhpOffice\PhpSpreadsheet\Exception
      */
-    public function prepare($cacheFile, $sortedHeaders, $freezeHeaders = false)
+    public function prepare($cacheFile, $sortedHeaders, $freezeHeaders = false, $flattenHeaders = false)
     {
-        $this->writeHeaders($sortedHeaders);
+        $this->writeHeaders($sortedHeaders, null, $flattenHeaders);
         if($freezeHeaders) {
-            $this->freezePanes();
+            //if $flattenHeaders true, freeze the rows above cell A2 (i.e row 1)
+            $flattenHeaders ? $this->freezePanes('A2') : $this->freezePanes();
         }
 
         $file = new \SplFileObject($cacheFile);
@@ -321,7 +339,7 @@ private function writeArray(array $row)
     public function freezePanes($cell = '')
     {
         if (empty($cell)) {
-            $cell = 'A3';
+            $cell = 'A3'; // A3 will freeze the rows above cell A3 (i.e row 2)
         }
         $this->spreadsheet->getActiveSheet()->freezePane($cell);
     }
diff --git a/test/Service/ExcelWriterTest.php b/test/Service/ExcelWriterTest.php
index f395b41..9082bec 100644
--- a/test/Service/ExcelWriterTest.php
+++ b/test/Service/ExcelWriterTest.php
@@ -95,7 +95,7 @@ public function testShouldWriteSingleRowHeaders()
         $this->buildService()->writeHeaders($headers);
     }
 
-    public function testShouldWriteNestedHeaders()
+    public function testShouldWriteNestedHeadersIfFlattenHeadersIsNotSet()
     {
         $columnDimensionMock = $this->getMockBuilder('\PhpOffice\PhpSpreadsheet\Worksheet\ColumnDimension')->disableOriginalConstructor()->getMock();
         $columnDimensionMock->expects($this->exactly(6))->method('setAutoSize')->with(true);
@@ -123,6 +123,32 @@ public function testShouldWriteNestedHeaders()
         $this->buildService()->writeHeaders($headers);
     }
 
+
+    public function testShouldWriteFlattenedNestedHeadersWithoutParentHeaderIfFlattenHeadersIsTrue()
+    {
+        $columnDimensionMock = $this->getMockBuilder('\PhpOffice\PhpSpreadsheet\Worksheet\ColumnDimension')->disableOriginalConstructor()->getMock();
+        $columnDimensionMock->expects($this->exactly(6))->method('setAutoSize')->with(true);
+
+        $phpExcelStyleMock2 = $this->getMockBuilder('\PhpOffice\PhpSpreadsheet\Style\Font')->disableOriginalConstructor()->getMock();
+        $phpExcelStyleMock2->expects($this->exactly(6))->method('setBold')->with(true);
+        $phpExcelStyleMock = $this->getMockBuilder('\PhpOffice\PhpSpreadsheet\Style\Style')->disableOriginalConstructor()->getMock();
+        $phpExcelStyleMock->expects($this->exactly(6))->method('getFont')->willReturn($phpExcelStyleMock2);
+
+        $worksheetMock = $this->getMockBuilder('\PhpOffice\PhpSpreadsheet\Worksheet\Worksheet')->disableOriginalConstructor()->getMock();
+        $worksheetMock->expects($this->exactly(6))->method('getStyle')->willReturn($phpExcelStyleMock);
+        $worksheetMock->expects($this->exactly(6))->method('setCellValue')->withConsecutive(
+            ['A1', 'Alpha'], ['B1', 'Bravo'], ['C1', 'Gamma'], ['D1', 'Delta'], ['E1', 'Foxtrot'], ['F1', 'Hotel']
+        );
+        $worksheetMock->expects($this->exactly(0))->method('mergeCells');
+        $worksheetMock->expects($this->exactly(6))->method('getColumnDimension')->withConsecutive(
+            ['A'], ['B'], ['C'], ['D'], ['E'], ['F']
+        )->willReturn($columnDimensionMock);
+        $this->spreadsheet->expects($this->once())->method('getActiveSheet')->willReturn($worksheetMock);
+
+        $headers = [0 => 'Alpha', 1 => 'Bravo', 2 => 'Gamma', 3 => 'Delta', 4 => ['Echo' => ['Foxtrot', 'Hotel']]];
+        $this->buildService()->writeHeaders($headers, null, true);
+    }
+
     public function testShouldWriteNonNestedData()
     {
         $input = [