Atmega16 not receiving complete response on serial from GSM sim300

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I am working on GSM sim300. I want to receive SMS on serial port of atmega16. When I send SMS " 23# "to gsm modem it send,
" \r\n+CMGR:\s"REC\sUNREAD","+919762148043",,"14/03/13,23:04:32+22"\r\n23#\r\n\r\nOK\r\n "
this string in response. I am parsing this string using this logic

while(Serial.available())
  {
    char tempChar = Serial.read();
    if(tempChar == '+')
    {
      isPreSms = true;
      lcd.print('+');
    }
    else if((tempChar == '\r') && (isPreSms == true))
    {
      isPreSms = false;
      lcd.print('r');
    }
    else if(tempChar == '*')
    {
      digitalWrite(OKLed, HIGH);
      isSms = true;
      lcd.print('*');
    }
    else if((tempChar == '#') && (isSms == true))
    {
      digitalWrite(powerLed, HIGH);
      isSms = false;
      lcd.print(sms);
    }
    else if(isSms)
    {
      digitalWrite(alertLed, HIGH);
      sms += tempChar;
    }
  }
  lcd.print('@');
}

I am expecting " +++r*23@" on my lcd display, but am getting only this " +++r@".
It means controller receive
" \r\n+CMGR:\s"REC\sUNREAD","+919762148043",,"14/03/13,23:04:32+22"\r\n "
this much of string. I am got stuck here. GSM send complete string(i verified that) but controller not receiving complete. Please help.