gsm module question

Is it possible to edit/replace the recipient for the gsm module where messages would be sent?

Yeah you can easily do that in your coding. AT+CMGS is the command used for sending message, you have to add the receiving number here, which you can change.

Here is my code but i the message doesnt get through my phone please help

#include <SoftwareSerial.h>
SoftwareSerial sim(10,11);//SIM800L==TX,RX
int _timeout;
String _buffer;
String coconum;
String editNo;
String number;
String newNumber;

bool bobo = true;
bool inside = true;
char decide;

void setup() {
  // put your setup code here, to run once:
  delay(10000);
  Serial.begin(9600);
  _buffer.reserve(50);
  sim.begin(9600);
  delay(1000);
  Serial.println("Now ready...");
}

void loop() {
  // put your main code here, to run repeatedly:
  enterNumber();
  delay(5000);
  
}

void enterNumber(){
  Serial.println("Enter 9-digit number...");
  while(bobo){
    if(Serial.available()){
      editNo = Serial.readString();
      bobo = false;}}
      newNumber = "+639" + editNo;
      String number = newNumber;
      Serial.print("Message to send to ");
      Serial.println(number);
    
     //Serial.println ("Sending Message");
  sim.println("AT+CMGF=1");    //Sets the GSM Module in Text Mode
  Serial.println("AT+CMGF=1");
  delay(1000);
  //Serial.println ("Set SMS Number");
  sim.println("AT+CMGS=\"" + number + "\"\r"); //Mobile phone number to send message
  Serial.println("AT+CMGS=\"" + number + "\"\r");
  delay(1000);
  String SMS = "Hello, how are you?";
  sim.println(SMS);
  Serial.println(SMS);
  delay(100);
  sim.println((char)26);// ASCII code of CTRL+Z
  delay(1000);
  _buffer = _readSerial();
  
}

String _readSerial() {
  _timeout = 0;
  while  (!sim.available() && _timeout < 12000  )
  {
    delay(13);
    _timeout++;
    Serial.println("Error");
  }
  if (sim.available()) {
    return sim.readString();
    Serial.println("Return");
  }
}
      String number = newNumber;

At this point you have 2 variables named number. Does that REALLY seem like a good idea?

You send several commands to the modem, but you only read ONE response. Why? Read ALL of them, and, just perhaps, a clue by four will whack you.

I done that when I realize that there are 2 number strings but it still doesnt work and ive done this because it says that the string number wasnt declared and it still doesnt work

#include <SoftwareSerial.h>
SoftwareSerial sim(10,11);//SIM800L==TX,RX
int _timeout;
String _buffer;
String coconum;
String editNo;
String newNumber;

bool bobo = true;
bool inside = true;
char decide;

void setup() {
  // put your setup code here, to run once:
  delay(10000);
  Serial.begin(9600);
  _buffer.reserve(50);
  sim.begin(9600);
  delay(1000);
  Serial.println("Now ready...");
}

void loop() {
  // put your main code here, to run repeatedly:
  enterNumber();
  delay(5000);
  
}

void enterNumber(){
  Serial.println("Enter 9-digit number...");
  while(bobo){
    if(Serial.available()){
      editNo = Serial.readString();
      bobo = false;}}
      newNumber = "+639" + editNo;
      String number = newNumber;
      Serial.print("Message to send to ");
      Serial.println(number);
    
     //Serial.println ("Sending Message");
  sim.println("AT+CMGF=1");    //Sets the GSM Module in Text Mode
  Serial.println("AT+CMGF=1");
  delay(1000);
  //Serial.println ("Set SMS Number");
  sim.println("AT+CMGS=\"" + number + "\"\r"); //Mobile phone number to send message
  Serial.println("AT+CMGS=\"" + number + "\"\r");
  delay(1000);
  String SMS = "Hello, how are you?";
  sim.println(SMS);
  Serial.println(SMS);
  delay(100);
  sim.println((char)26);// ASCII code of CTRL+Z
  delay(1000);
  _buffer = _readSerial();
  
}

String _readSerial() {
  _timeout = 0;
  while  (!sim.available() && _timeout < 12000  )
  {
    delay(13);
    _timeout++;
    Serial.println("Error");
  }
  if (sim.available()) {
    return sim.readString();
    Serial.println("Return");
  }
}

You are still writing several commands to the sim device, and only reading ONE response, and then not printing that.

When you grasp the concept that the first command you write to the device can result in an error, rendering any following commands meaningless, and you read AND PRINT the reply to EVERY command, you'll be able to make progress.

Until then, feel free to keep pounding your head against the wall. But, stop complaining about getting a headache.