[SOLVED] PIC serial port receive Problem, please help

// adjust this to the length of the longest response + 1
#define BUFFERSIZE 20 

// this is the ISR
void __interrupt() ISR(void)
{
  if(PIR1bits.RCIF)
  {
    if(RCSTAbits.OERR)
    {
      RCSTAbits.CREN = 0;
      RCSTAbits.CREN = 1;
    }
    else
    {
      ByteReceived = RXREG;
      gsmFlag = 1;
    }
}

// this is in your main loop
if(gsmFlag)
{
  if(ByteReceived == '+') GSMindex = 0;   // start of message found
  if(ByteReceived == '\n') STAT = !STAT;  // or whatever you want to do with the data
  else
  {
    if(GSMindex < BUFFERSIZE) 
    {
      GSMbuff[GSMindex++] = ByteReceived;
      GSMbuff[GSMindex] = 0;
    }
  }
}

else  
    {
     GSMindex = 0;
    }

/******************************************************************************/
/* Files to Include                                                           */
/******************************************************************************/
#include <xc.h>             /* XC8 General Include File */
#include <stdint.h>         /* For uint8_t definition */
#include <stdbool.h>        /* For true/false definition */
#include "system.h"         /* System funct/params, like osc/peripheral config */
#include "user.h"           /* User funct/params, such as InitApp */
#include "lcd.h"            /* LCD functions*/
#include "usart.h"          /* Serial Port Functions*/
/******************************************************************************/
/* User Global Variable Declaration                                           */
/******************************************************************************/
unsigned char pass[MAX_PASS_LEN],regPhoneNumber[MAX_PHONE_LEN+1],regIbId[MAX_IBID_LEN]; 
/******************************************************************************/
/* Main Program                                                               */
/******************************************************************************/
void main(void){
    unsigned char temp,data;
    unsigned long timeout = 1500000;
    /* Initialize I/O and Peripherals for application */
    InitApp();
    STAT = false;
    lcd_clear();
    lcd_goto(0X00);
    lcd_puts("GSM Debug");
    lcd_goto(0X40);
    temp = 3;   //three retries
    do{ 
        lcd_goto(0X00);
        lcd_puts("ATE0 SENT...");
        lcd_goto(0X40);
        data = gsmTest();
        flushGsmBuff();
        lcd_putXnum(data);
        lcd_putch(',');
        if(data)
            break;
        temp--;
        
    }while(!data);
    lcd_goto(0X40);
    lcd_puts("WAITING FOR SMS");
    
    putstr("AT+CMGF=1\r");
    __delay_ms(1000);
    putstr("AT+CMGD=0\r");
    __delay_ms(1000);
    putstr("AT+CNMI=2,2,0,0,0\r");
    __delay_ms(1000);
    PIR1bits.RCIF = 0;
    PIE1bits.RCIE = 1;
    INTCONbits.PEIE = 1;
    INTCONbits.GIE = 1;
    lcd_clear();
    lcd_goto(0x00);
    GSMindex = 0;
    gsmFlag = 0;
    while(1){
        if(gsmFlag){
            STAT = true;
            while(1){
                if(GSMbuff[GSMindex - 1] == EOD){
                    gsmFlag = 0;
                    break;
                }
                if(GSMindex >= MAX_BUF_LEN)
                    break;
                timeout --;
                if(!timeout)
                    break;
            }
            STAT = false;
            lcd_putch('*');
            __delay_ms(500);
            PIE1bits.RCIE = 0;
            lcd_clear();
            lcd_goto(0X00);
            temp = GSMindex;
            GSMindex = 0;
            while(GSMindex < temp){
                lcd_putch(GSMbuff[GSMindex]);
                GSMindex ++;
                if(GSMindex%60 == 0){
                    lcd_goto(0X54);
                }
                else if(GSMindex%40 == 0){
                    lcd_goto(0X14);
                }
                else if(GSMindex%20 == 0){
                    lcd_goto(0X40);
                }
            }
            lcd_putXnum(temp);
            GSMindex = 0;
            timeout = 1500000;
            gsmFlag = 0;
        }
    }
}