interfacing duemilanove with gsm sim900

i ve been trying to send a mess thru sim900 gsm/gprs sim900 modem using arduino duemilanove…

i ve edited the example program from the following link

http://www.seeedstudio.com/wiki/GPRS_Shield_V1.0

my final code is as below:

#include <SoftwareSerial.h>
#include <String.h>

SoftwareSerial mySerial(7, 8);

void setup()
{
mySerial.begin(9600); // the GPRS baud rate
Serial.begin(9600); // the GPRS baud rate
delay(50);
}
void loop()
{
//after start up the program, you can using terminal to connect the serial of gprs shield,
//if you input ‘t’ in the terminal, the program will execute SendTextMessage(), it will show how to send a sms message,
//if input ‘d’ in the terminal, it will execute DialVoiceCall(), etc.

if (Serial.available())
switch(Serial.read())
{
case ‘t’:
SendTextMessage();
break;
}

if (mySerial.available())
Serial.write(mySerial.read());
}
void SendTextMessage()
{
mySerial.print(“AT+CMGF=1\r”); //Because we want to send the SMS in text mode
delay(100);
mySerial.println("AT + CMGS = “+9180895537796"”);//send sms message, be careful need to add a country code before the cellphone number
delay(100);
mySerial.println(“A test message!”);//the content of the message
delay(100);
// mySerial.println((char)26);//the ASCII code of the ctrl+z is 26
// delay(100);
mySerial.println();
}
void ShowSerialData()
{
while(mySerial.available()!=0)
Serial.write(mySerial.read());
}

i ve followed al steps mentioned in the above link.
once i upload tis code n open up serial monitor n turn on the gps modem… i get the following output which is also attached below in the attachments…

" yyyyyyyy
RDY
+CFUN:1
+CPIN:READY
call ready"

thats it… after tis there’s no response at al… it dsnt give any error or anything but just remains still for infinitye time… pls suggest smthng…