Well after a long time troubleshooting i found that problem was that i was not using delay function after AT commands.
Working code enjoy 
#include<String.h>
int temp4=0;
int lenth,lenth1,i=0,temp=0;
String str="";
String nam="";
String number="";
String m="Status";
void setup() {
pinMode (9,OUTPUT);
Serial3.begin(9600);
Serial.begin(9600);
Serial3.println("AT+CNMI=2,2,0,0,0");
Serial3.println("AT+CMGF=1");
delay(100);
if (Serial3.available()>0)
Serial.write(Serial3.read());
}
void loop()
{
while(temp!=0)
{
i=0;
while(i<lenth)
{
if(str=='"')
{
temp4++;
}
if(temp4==1)
{
for(int j=0;j<15;j++)
{
number+=str;
i++;
}
temp4=2;
}
if(str=='*')
{
i++;
while(str!='#')
{
nam+=str;
i++;
}
}
i++;
}
Serial.print(nam);
if (nam.compareTo(m)==0)
{
SendMessage();
}
delay(2000);
temp=0;
temp4=0;
nam="";
lenth=0;
str="";
number="";
delay(1000);
}
}
void serialEvent3()
{
while (Serial3.available())
{
char inChar = (char)Serial3.read();
str+=inChar;
lenth++;
if (inChar == 'n')
{ temp=1;
inChar=0;
}
}
}
void SendMessage()
{
digitalWrite(9,HIGH);
Serial3.println("AT+CMGF=1"); //Sets the GSM Module in Text Mode
delay(1000); // Delay of 1000 milli seconds or 1 second
Serial3.println("AT+CMGS="+918557803648"r"); // Replace x with mobile number
delay(1000);
Serial3.println("I am SMS from GSM Module");// The SMS text you want to send
delay(100);
Serial3.println((char)26);// ASCII code of CTRL+Z
delay(100);
}