GSM-SIM800LV2.2 + ARDUINO UNO + STC

#include <SoftwareSerial.h>

//SIM800L TX is connected to Arduino D3
#define SIM800L_TX_PIN 7

//SIM800L RX is connected to Arduino D2
#define SIM800L_RX_PIN 6

//Create software serial object to communicate with SIM800L
SoftwareSerial serialSIM800L(SIM800L_TX_PIN, SIM800L_RX_PIN);

void setup() {
  //Begin serial comunication with Arduino and Arduino IDE (Serial Monitor)
  Serial.begin(9600);
  while (!Serial);

  //Being serial communication witj Arduino and SIM800L
  serialSIM800L.begin(9600);
  delay(1000);
  Serial.println("Setup Complete!");

  delay(15000);
  Serial.println("Sending Text...");
  serialSIM800L.print("AT+CMGF=1\r"); // Set the shield to SMS mode
  delay(100);

  serialSIM800L.print("AT+CMGS=\"0551234567\"\r");
  delay(200);

  serialSIM800L.print("This is a message from DAWAER's Arduino!");
  serialSIM800L.print("\r"); //the content of the message
  delay(500);

  serialSIM800L.print((char)26);//the ASCII code of the ctrl+z is 26 (required according to the datasheet)
  delay(100);

  serialSIM800L.println();

  Serial.println("Text Sent.");
  delay(500);


}

void loop() {
  //Read SIM800L output (if available) and print it in Arduino IDE Serial Monitor
  if (serialSIM800L.available()) {
    Serial.write(serialSIM800L.read());
  }
  //Read Arduino IDE Serial Monitor inputs (if available) and send them to SIM800L
  if (Serial.available()) {
    serialSIM800L.write(Serial.read());
  }
}