GSM Shield does not work with MEGA 2560 and UNO arduino.

I am a novice user of Arduino.I purchased Mega 2560 and GSM Shield 2(without any antennae attached,as M10 has inbuilt antennae),I wish to run certain examples from GSM library but none of it shows satisfactory resultSo I thought of purchasing UNO,I bought that but the GSM shield doesnot work with it aswell.

Tried below example ;result =SMS Messages Sender
Not Connected.
What all I have tried:

  • Downloading version 1.6 and installing tinysine GSM library and decommenting uno while using MEga 2560 ;
    *Applying external power supply(12V and 2 A) along with USB connected ;
    *For MEGA : USING A JUMPER FORM 2 TO 10 PIN and disconnecting male header from connecting to Mega board;
    *Uploading Pin no. ,APN ,login and user I.d;
    *UPloading using AT commands aswell;
    *Switching Power button ON on GsM shield after the code has been uploaded,

I need Urgent assistance as my project is due because of this issue.
kindly assist as soon as possible.
I am attching the code that I am using please guide me as soon as possible.

/*
 SMS sender

 This sketch, for the Arduino GSM shield,sends an SMS message
 you enter in the serial monitor. Connect your Arduino with the
 GSM shield and SIM card, open the serial monitor, and wait for
 the "READY" message to appear in the monitor. Next, type a
 message to send and press "return". Make sure the serial
 monitor is set to send a newline when you press return.

 Circuit:
 * GSM shield
 * SIM card that can send SMS

 created 25 Feb 2012
 by Tom Igoe

 This example is in the public domain.

 http://www.arduino.cc/en/Tutorial/GSMExamplesSendSMS

 */

// Include the GSM library
#include <GSM.h>

#define PINNUMBER "0000"

// initialize the library instance
GSM gsmAccess;
GSM_SMS sms;

void setup() {
  // initialize serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  Serial.println("SMS Messages Sender");

  // connection state
  boolean notConnected = true;

  // Start GSM shield
  // If your SIM has PIN, pass it as a parameter of begin() in quotes
  while (notConnected) {
    if (gsmAccess.begin(PINNUMBER) == GSM_READY) {
      notConnected = false;
    } else {
      Serial.println("Not connected");
      delay(1000);
    }
  }

  Serial.println("GSM initialized");
}

void loop() {

  Serial.print("Enter a mobile number: ");
  char remoteNum[20];  // telephone number to send sms
  readSerial(remoteNum);
  Serial.println(remoteNum);

  // sms text
  Serial.print("Now, enter SMS content: ");
  char txtMsg[200];
  readSerial(txtMsg);
  Serial.println("SENDING");
  Serial.println();
  Serial.println("Message:");
  Serial.println(txtMsg);

  // send the message
  sms.beginSMS(remoteNum);
  sms.print(txtMsg);
  sms.endSMS();
  Serial.println("\nCOMPLETE!\n");
}

/*
  Read input serial
 */
int readSerial(char result[]) {
  int i = 0;
  while (1) {
    while (Serial.available() > 0) {
      char inChar = Serial.read();
      if (inChar == '\n') {
        result[i] = '\0';
        Serial.flush();
        return 0;
      }
      if (inChar != '\r') {
        result[i] = inChar;
        i++;
      }
    }
  }
}