sms_reply through gsm

Hardware Arduino GSM Shield
1

I was trying to send a reply sms to the sender's number. For this, I tried to run the combined code of sendSMS and receiveSMS given in the arduino examples. But it pauses in one of the command and do not run completely. Kindly someone look into the matter and suggest changes.
Here is the code:

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

// PIN Number for the SIM
#define PINNUMBER ""

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

// Array to hold the number a SMS is retreived from
char senderNumber[20];

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 Receiver");

// connection state
boolean notConnected = true;

// Start GSM connection
while (notConnected) {
if (gsmAccess.begin(PINNUMBER) == GSM_READY) {
notConnected = false;
} else {
Serial.println("Not connected");
delay(1000);
}
}

Serial.println("GSM initialized");
Serial.println("Waiting for messages");
}

void loop() {
char c;

// If there are any SMSs available()
if (sms.available()) {
Serial.println("Message received from:");

// Get remote number
sms.remoteNumber(senderNumber, 20);
Serial.println(senderNumber);

delay(1000);

// 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(senderNumber);
sms.print(txtMsg);
sms.endSMS(); // this program pauses here in the serial monitor
Serial.println("\nCOMPLETE!\n");

// An example of message disposal
// Any messages starting with # should be discarded
if (sms.peek() == '#') {
Serial.println("Discarded SMS");
sms.flush();
}

// Read message bytes and print them
while (c = sms.read()) {
Serial.print(c);
}

Serial.println("\nEND OF MESSAGE");

// Delete message from modem memory
sms.flush();
Serial.println("MESSAGE DELETED");
}

delay(1000);

}