Arduino duemilanove + Sim900d + LED light [HELP]

Hello Sir/Maam Good day!
im having problem with the codes. i want to lights on the LED when i text gsm module “x” and turn it of when i text it “o”. led is in pin 13. no error in program when i compile it but when i text the gsm module no output response.
heres my program…

#include <SoftwareSerial.h>
#include <string.h>
char inchar;
SoftwareSerial cell(2,3);
int led1 = 13;
void setup()
{
  
  digitalWrite(powerOn, HIGH); 
  delay(1500);
  digitalWrite(powerOn, LOW);
  delay(5000);
 
  pinMode(led1, OUTPUT);
  digitalWrite(led1, LOW);
 
  Serial.begin(9600);
  cell.begin(9600);
  delay(30000);
  Serial.println("Unit Started");
 
  cell.println("AT+CMGF=1"); // set SMS mode to text
  delay(200);
  cell.println("AT+CNMI=1,2,0,0,0 "); // set module to send SMS data to serial out upon receipt
  delay(200);
}
void loop()
{
  while(cell.available() >0)
  {
  inchar=cell.read();
  Serial.print(inchar);
    if (inchar=='x')
    {
      digitalWrite(led1, HIGH);
    }
    else if (inchar=='o')
    {
      digitalWrite(led1, LOW);
    }
    delay(10);
 
  }
}

thank you for helping and God bless.

Moderator edit:
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</mark> <mark>[/code]</mark> <mark>
tags added.

  Serial.print(inchar);

Are you seeing 'x' or 'o' in the serial monitor?

thx for the reply sir…

no x or o for serial monitor sir…
only squares

The code you posted won't even compile. powerOn is not defined anywhere.

  cell.println("AT+CMGF=1"); // set SMS mode to text

And the phone's response is?

  cell.println("AT+CNMI=1,2,0,0,0 "); // set module to send SMS data to serial out upon receipt

And the phone's response is?

  inchar=cell.read();
  Serial.print(inchar);

Why is inchar a global variable? You might want to add ,HEX to the print statement, to see what the phone actually sent.

    delay(10);

Why?