String messageFromSIMmodule = "Start 1981";
int h;
String autoStart_S;
int autoStart_I;

void setup() {

Serial.begin(9600);
Serial.println("BEGIN");
Serial.println();

pinMode(27, INPUT_PULLUP);
pinMode(34, INPUT_PULLUP);

}

void loop() {

if (messageFromSIMmodule.indexOf("Start") != -1) {
  autoStart_S = "";
  h=0;
  while (h < messageFromSIMmodule.length()) {
    if (isDigit(messageFromSIMmodule[h])) {
      autoStart_S = autoStart_S + messageFromSIMmodule[h];
    }
    h++;
  }
  messageFromSIMmodule = "";
  autoStart_I = autoStart_S.toInt();
}

Serial.print("autoStart_I ");
Serial.println(autoStart_I);
Serial.print("messageFromSIMmodule ");
Serial.println(messageFromSIMmodule);

delay(2000);

if (digitalRead(27) == LOW) {
  messageFromSIMmodule = "Start 719817";
}

if (digitalRead(34) == LOW) {
  messageFromSIMmodule = "Start 5555";
}

}