Problem with Arduino and GPRS shield v2

[size=150]Using GPRS Shield With Mega[/size]

1. Connect pin-7 to pin-10 (pin-8 to pin-11) by jumper wire
2. Use this code:

#include <SoftwareSerial.h>
 
SoftwareSerial GPRS(10, 11);
unsigned char buffer[64]; // buffer array for data recieve over serial port
int count = 0;     // counter for buffer array 

void setup()
{
    GPRS.begin(19200);               // the GPRS baud rate   
    Serial.begin(19200);             // the Serial port of Arduino baud rate.
}
 
void loop()
{
    if (GPRS.available())              // if date is comming from softwareserial port ==> data is comming from gprs shield
    {
        while (GPRS.available())          // reading data into char array 
        {
            buffer[count++] = GPRS.read();     // writing data into array
            if (count == 64)
                break;
        }
        Serial.write(buffer, count);            // if no data transmission ends, write buffer to hardware serial port
        clearBufferArray();              // call clearBufferArray function to clear the storaged data from the array
        count = 0;                       // set counter of while loop to zero
    }
    if (Serial.available())            // if data is available on hardwareserial port ==> data is comming from PC or notebook
        GPRS.write(Serial.read());       // write it to the GPRS shield
}

void clearBufferArray()              // function to clear buffer array
{
    for (int i=0; i < count; i++)
    {
        buffer[i] = NULL;
    }                               // clear all index of array with command NULL
}

3. Go AT command tester describe in product wiki, Connect with 19200 bps
   Note:Don’t forget to plug the jumpers to SWserial mode.
   Good luck!