[PIC] Need a help on PIC18f4550 and SIM300S

/********************************************************************/

#include "Lcd.h"
#include "General.h"
#include "DisplayMacros.h"

#include <p18f4550.h>
#include <delays.h>
	

#define FREQ 		12000000
#define BAUD 		9600
#define SPBRG_VALUE (((FREQ/64)/BAUD)-1)
#define PB1	PORTAbits.RA4
#define PB2	PORTBbits.RB0


void Wait2s(void);					///< 2s delay used to display splash screen
void Wait1s(void);

void DisplaySplashText(void);				      ///< Display the welcome Text
void StateInitial(void);					           ///< Go to initial state

void gsmCode(void);
/*void gsmInit(void);
void gpsCode(void);
void gpsInit(void); */

unsigned char rx_data(void);
void tx_data(unsigned char);
void gsm_cmd(unsigned char *);
void output(void);
void interrupt(void);


unsigned char value = 0;
int i = 0,j,k,temp,flag;
unsigned char *starting_text = "Enter Choice =";
unsigned char *dial_text = "Dialing...";
unsigned char *at_cmd = "AT";
unsigned char *imei_cmd = "AT+GSN";
unsigned char *call_cmd = "ATDxxxxxxxxxx"; // Provide a 10-Digit Mobile Number
unsigned char *sms_format = "AT+CMGF=1";
unsigned char *sms_write = "AT+CMGS=\"xxxxxxxxxx\""; // 10-Digit Mobile Number
unsigned char *sms = "Hello";
unsigned char *sms_report = "SMS Sent...";
unsigned char sms_terminate = 0x1A;
unsigned char enter = 0x0D;

unsigned char *data;

unsigned char longi_data[12];
unsigned char lati_data[12];

void main(void)
{ 
  TRISA = 0xFF;
  TRISB = 0xF1;
  TRISC = 0x80;
  TRISD = 0x00;
  SPBRG = SPBRG_VALUE; 		// Fill SPBRG register to set the baud rate
  RCSTAbits.SPEN = 1; 		// To activate serial port (Tx and Rx pins)
  TXSTAbits.TXEN = 1; 		// Activate Transmissiom
  RCSTAbits.CREN = 1; 		// Activate Reception
  PIE1bits.RCIE = 1; 		// Enable Reception interrupt
  INTCONbits.GIE = 1;       // Peripheral Interrupt enable
  INTCONbits.PEIE = 1;      // General Interrupt enable
  
  LATA = 0; LATB = 0; LATC = 0; LATD = 0; 
  LCDInit();
 
  gsmCode();
  
}	// End of main function


void gsmCode(void)
{
  while(1)		// Main Infinite loop
  {                 
	StateInitial();

	if(!PB1)
	{
		PORTBbits.RB1 = 1;
		gsm_cmd(at_cmd);
		output();
		Wait1s();
	}	

	if(!PB2)
	{
		LATB = 0;
		PORTBbits.RB2 = 1; 
		gsm_cmd(sms_format);
		output(); 
		Wait1s();
	
		gsm_cmd(sms_write);
		output();
		Wait1s();

		gsm_cmd(sms);
		output();
		tx_data(sms_terminate);  // Send ASCII code for 'Ctrl+z' key
		Wait1s();
	}
  }		// Main infinite loop
}


void gsm_cmd(unsigned char *string)
{
i = 0; j = 0; temp = 0;
while(string[i] != '\0')
{
temp = 0;
if(string[i] == 0x5C) // Not to send '\' character
i++;
tx_data(string[i]); // Send by serial communication
i++;
while(temp != 1);
}
tx_data(enter); // Send ASCII code for 'Enter' key
interrupt();
while(temp != 1);
}


void output(void) // To print data on LCD
{
i = 0; flag = 0;  
LCDClear();		// Clear LCD for next display
while(i < j)
{
if(flag > 1)
{
flag = 0;
Delay10KTCYx(10);	// 500ms delay
LCDClear();		// Clear LCD for next display
LCDGoto(0,0);
}

/* This condition is to avoid double Enter during execution of a command */
if(data[i] == 0x0A)
{
flag++;
LCDGoto(0,1);
}

/* Not to print this character */
if(data[i]=='>' || data[i]=='"') 
{
i++;
LCDGoto(0,1);
}

/* Condition to print the data, except 'Enter','New line' and 'Submit' */
if(data[i]!=0x0D && data[i]!=0x0A && data[i]!=0x1A) 
{
LCDPutChar(data[i]);
i++;
}
else
i++;

Delay10KTCYx(6);	// 300ms delay
}

LCDClear();		// Clear LCD for next display
}


void tx_data(unsigned char serial_data) // Transmit data function
{
  TXREG = serial_data;
  while(PIR1bits.TXIF == 0);
}


void interrupt(void)
{
data[j] = RCREG; // Store the data into array when Reception interrupt occurs
value = data[j];
j++;
temp = 1;
}


void StateInitial(void)
{
	DisplaySplashText();                // Welcome message
	Wait2s();                  			// Leave splash screen for 2 s
}


void DisplaySplashText(void)
{
  	LCDClear();
	WELCOME();
}


void Wait2s(void)
{
	Delay10KTCYx(40);
}

void Wait1s(void)
{
	Delay10KTCYx(20);
}