How to transfer data in two VCPs with DUAL CDC composite device

I have emulated two VCPs with only one USB Device. I can send data in one VCP that has the following Endpoint Address.

#define CDC_IN_EP                                   0x81  /* EP1 for data IN */
#define CDC_OUT_EP                                  0x01  /* EP1 for data OUT */
#define CDC_CMD_EP                                  0x82  /* EP2 for CDC commands */

I would like to know if it's possible to send data in the other VCP with other Endpoint Address like :

#define CDC_IN_EP3                                   0x83  /* EP3 for data IN */
#define CDC_OUT_EP3                                  0x03  /* EP3 for data OUT */
#define CDC_CMD_EP4                                  0x84  /* EP4 for CDC commands */

My problem is that addresses others than 0x81 don't allow me to send data over the second VCP. I'm using two CDC interfaces Full-Speed (Dual CDC Composite Device). Normally we can use 7 endpoints with CDC_FS and that's what I'm trying to do.. I have 6 Endpoints: 3 for each VCP and the seventh is Endpoint 0 for configuration.

Have I missed something in the Endpoints Configuration or in the Composite Device Descriptors ?

/* USB CDC device Configuration Descriptor */
__ALIGN_BEGIN uint8_t USBD_CDC_CfgFSDesc[USB_CDC_CONFIG_DESC_SIZ] __ALIGN_END =
{
  /*Configuration Descriptor*/
  0x09,   /* bLength: Configuration Descriptor size */
  USB_DESC_TYPE_CONFIGURATION,      /* bDescriptorType: Configuration */
  USB_CDC_CONFIG_DESC_SIZ,                /* wTotalLength:no of returned bytes */
  0x00,
  0x04,   /* bNumInterfaces: 4 interface */
  0x01,   /* bConfigurationValue: Configuration value */
  0x00,   /* iConfiguration: Index of string descriptor describing the configuration */
  0xC0,   /* bmAttributes: self powered */
  0x32,   /* MaxPower 100 mA */

  /*---------------------------------------------------------------------------*/

                // IAD0
        0x08,   // bLength: Interface Descriptor size
        0x0B,   // bDescriptorType: IAD
        0x00,   // bFirstInterface    OR 0x02 for the second IAD
        0x02,   // bInterfaceCount
        0x02,   // bFunctionClass: CDC
        0x02,   // bFunctionSubClass
        0x01,   // bFunctionProtocol
        0x02,   // iFunction

  /*Interface0 Descriptor */
  0x09,   /* bLength: Interface Descriptor size */
  USB_DESC_TYPE_INTERFACE,  /* bDescriptorType: Interface */
  /* Interface descriptor type */
  0x00,   /* bInterfaceNumber: Number of Interface */
  0x00,   /* bAlternateSetting: Alternate setting */     OR 0x02 for the second IAD
  0x01,   /* bNumEndpoints: One endpoints used */
  0x02,   /* bInterfaceClass: Communication Interface Class */
  0x02,   /* bInterfaceSubClass: Abstract Control Model */
  0x01,   /* bInterfaceProtocol: Common AT commands */
  0x00,   /* iInterface: */

  /*Header Functional Descriptor*/
  0x05,   /* bLength: Endpoint Descriptor size */
  0x24,   /* bDescriptorType: CS_INTERFACE */
  0x00,   /* bDescriptorSubtype: Header Func Desc */
  0x10,   /* bcdCDC: spec release number */
  0x01,

  /*Call Management Functional Descriptor*/
  0x05,   /* bFunctionLength */
  0x24,   /* bDescriptorType: CS_INTERFACE */
  0x01,   /* bDescriptorSubtype: Call Management Func Desc */
  0x03,   /* bmCapabilities: D0+D1 */
  0x01,   /* bDataInterface: 1 */

  /*ACM Functional Descriptor*/
  0x04,   /* bFunctionLength */
  0x24,   /* bDescriptorType: CS_INTERFACE */
  0x02,   /* bDescriptorSubtype: Abstract Control Management desc */
  0x02,   /* bmCapabilities */

  /*Union Functional Descriptor*/
  0x05,   /* bFunctionLength */
  0x24,   /* bDescriptorType: CS_INTERFACE */
  0x06,   /* bDescriptorSubtype: Union func desc */
  0x00,   /* bMasterInterface: Communication class interface */
  0x01,   /* bSlaveInterface0: Data Class Interface */


  /*Endpoint 2 Descriptor*/
  0x07,                           /* bLength: Endpoint Descriptor size */
  USB_DESC_TYPE_ENDPOINT,   /* bDescriptorType: Endpoint */
  CDC_CMD_EP,                     /* bEndpointAddress */   OR  CDC_CMD_EP4 for the second IAD
  0x03,                           /* bmAttributes: Interrupt */
  LOBYTE(CDC_CMD_PACKET_SIZE),     /* wMaxPacketSize: */
  HIBYTE(CDC_CMD_PACKET_SIZE),
  0xFF,                           /* bInterval: */
  /*---------------------------------------------------------------------------*/

  /*Data class interface descriptor*/
  0x09,   /* bLength: Endpoint Descriptor size */
  USB_DESC_TYPE_INTERFACE,  /* bDescriptorType: */
  0x01,   /* bInterfaceNumber: Number of Interface */   OR 0x03 for the second IAD
  0x00,   /* bAlternateSetting: Alternate setting */
  0x02,   /* bNumEndpoints: Two endpoints used */
  0x0A,   /* bInterfaceClass: CDC */
  0x00,   /* bInterfaceSubClass: */
  0x00,   /* bInterfaceProtocol: */
  0x00,   /* iInterface: */

  /*Endpoint OUT Descriptor*/
  0x07,   /* bLength: Endpoint Descriptor size */
  USB_DESC_TYPE_ENDPOINT,      /* bDescriptorType: Endpoint */
  CDC_OUT_EP,                  /* bEndpointAddress */   OR CDC_OUT_EP3 for the second IAD
  0x02,                              /* bmAttributes: Bulk */
  LOBYTE(CDC_DATA_FS_MAX_PACKET_SIZE),  /* wMaxPacketSize: */
  HIBYTE(CDC_DATA_FS_MAX_PACKET_SIZE),
  0x00,                              /* bInterval: ignore for Bulk transfer */

  /*Endpoint IN Descriptor*/
  0x07,   /* bLength: Endpoint Descriptor size */
  USB_DESC_TYPE_ENDPOINT,      /* bDescriptorType: Endpoint */
  CDC_IN_EP,                 /* bEndpointAddress */   OR CDC_OUT_EP3 for the second IAD
  0x02,                              /* bmAttributes: Bulk */
  LOBYTE(CDC_DATA_FS_MAX_PACKET_SIZE),  /* wMaxPacketSize: */
  HIBYTE(CDC_DATA_FS_MAX_PACKET_SIZE),
  0x00,                               /* bInterval: ignore for Bulk transfer */

} ;

Thank you guys.