CustomerAtCmdSend() give ERROR Response

Legacy Open AT
5 
s16 CustomerATcommandSubscription ( void )
{
    /* Subscribe to the 'AT+CUSTOMER' command. */
    s16 s16Return = adl_atCmdSubscribe( "AT+CUSTOMER",
                                        ( adl_atCmdHandler_t )ATCmdCustomer_Handler,
                                        ADL_CMD_TYPE_READ | ADL_CMD_TYPE_TEST |
                                        ADL_CMD_TYPE_PARA | 0x11 );
    TRACE( ( APPLI_AT_CMD_TRACE_LEVEL, "Customer command subscription %d", s16Return ) );
    if ( 0 > s16Return )
    {
        TRACE( ( APPLI_AT_CMD_TRACE_LEVEL, "Customer command subscription failed !") );
    }
    return s16Return;
}

the function ATCmdCustomer_Handler is defined as

void ATCmdCustomer_Handler ( adl_atCmdPreParser_t *paras )
{
    TRACE( ( APPLI_AT_CMD_TRACE_LEVEL, "ATCmdCustomer_Handler: Response handled" ) );
    TRACE( ( APPLI_AT_CMD_TRACE_LEVEL, paras->StrData ) );

    /*
     * When this handler is called, the customer command (here 'AT+CUSTOMER?' was sent by the
     * Open AT® application).
     * The specific customer command treatment could be inserted or called in this handler
     * Because the subscription was made only on the READ syntax, this handler is called
     * only if the command is 'AT+CUSTOMER?". It 'AT+CUSTOMER=?' command is sent by the application,
     * the response will be ERROR and this handler is not called.
     */

    /*
     * Command treatment:
     * Because the subscription was only made on the READ type command, a +CUSTOMER response is returned
     */
    if ( ADL_CMD_TYPE_READ == paras->Type )
    {
        adl_atSendResponsePort( ADL_AT_INT,
                                paras->Port,
                                "\r\nCUSTOMER RESPONSE\r\n" );
        adl_atSendStdResponseSpe ( ADL_AT_PORT_TYPE ( paras->Port, ADL_AT_RSP ),
                                   ADL_STR_OK,
                                   paras->NI );
    }

}

The function CustomerATcommandSend () defined as

void CustomerATcommandSend ( void )
{
    s8 s8Return = 0;
    /*
     * We send the 'AT+CUSTOMER?' and subscribe to its responses with the adl_atCmdSendExt API.
     * Because this command is subscribed by the Open AT® command and is not supported by the Sierra
     * Wireless stack, the adl_atCmdSendExt API has to be used and the 3rd parameter (NI)
     * has to be set to ADL_NI_LAUNCH.
     * Others value for this parameter will request to treat this command by the stack, and an ERROR will
     * be returned by the Sierra Wireless stack because this command is not supported.
     * This is the method in order to create a specific AT command in an Open AT® application
     * and to call it by the application itself.
     * Moreover, the application can specify on which port the command has to be sent (in this
     * case, the command will be sent on the internal port between ADL and the Sierra Wireless stack.
     */
    TRACE( ( APPLI_AT_CMD_TRACE_LEVEL, "Send 'AT+CUSTOMER?' using the adl_atCmdSendExt API") );
    s8Return = adl_atCmdSendExt( "AT+CUSTOMER?",
                                 //ADL_PORT_OPEN_AT_VIRTUAL_BASE,
                                 ADL_PORT_UART1,
                                 ADL_NI_LAUNCH,
                                 NULL,
                                 ( adl_atRspHandler_t ) ATCmdCustomer_Response_Handler,
                                 "*",
                                 NULL );

    if ( 0 > s8Return )
    {
        TRACE( ( APPLI_AT_CMD_TRACE_LEVEL, "CustomerATcommandSend: error in adl_atCmdSendExt: %d", s8Return ) );
    }
}

The function ATCmdCustomer_Response_Handler() is defined as

s16 ATCmdCustomer_Response_Handler ( adl_atResponse_t *paras )
{
    TRACE( ( APPLI_AT_CMD_TRACE_LEVEL, "ATCmdCustomer_Response_Handler: Response handled" ) );
    TRACE( ( APPLI_AT_CMD_TRACE_LEVEL, paras->StrData ) );
    return FALSE;
}

while calling CustomerATcommandSend ()function it receives ERROR response only
can you explain
the code which i have used given in the samples at_cmd_service

Thanks