Arduino DS3231 alarms and SIM900

Hello, i’m trying to make a project which need to be on power save mode as possible.I use an arduino pro mini that is in sleep mode and an RTC DS3231 send an interrupt at the alarm that i set to then wake up do some work and then go to sleep.Everything works fine with the alarms and the code except the SIM900 parts which i need to send an sms with some sensor values.It seems that it skips completely the sms part.If someone could help would be nice.Here is a sample code :

#include <avr/sleep.h>
#include <Wire.h>
#include <RTClibExtended.h>
#include <SoftwareSerial.h>
#include <DHT.h>;

#define interruptPin 2 //Pin we are going to use to wake up the Arduino
#define relay 4
#define ledPin 13 
#define DHTPIN 12     // what pin we're connected to
#define DHTTYPE DHT22   // DHT 22  (AM2302)

DHT dht(DHTPIN, DHTTYPE); //// Initialize DHT sensor for normal 16mhz Arduino
RTC_DS3231 RTC;      //we are using the DS3231 RTC
SoftwareSerial mySerial(6, 5); //SIM800L Tx & Rx is connected to Arduino #6 & #5

float hum;  //Stores humidity value
float therm_mesa; //Stores temperature value

void setup() {


  pinMode(ledPin, OUTPUT);
  digitalWrite(ledPin, HIGH);
  digitalWrite(ledPin, LOW);
  pinMode(relay, OUTPUT);
  digitalWrite(relay, LOW);

  //Initialize communication with the clock
  RTC.adjust(DateTime(__DATE__, __TIME__));   //set RTC date and time to COMPILE time
  //clear any pending alarms
  RTC.armAlarm(1, false);
  RTC.alarmInterrupt(1, false);
  RTC.armAlarm(2, false);
  RTC.alarmInterrupt(2, false);


  //Set alarm1 every day at 18:33
  RTC.setAlarm(ALM1_MATCH_HOURS, 41, 1, 0);   //set your wake-up time here//  SETUP:  minutes/hours/seconds
 // RTC.setAlarm(ALM2_MATCH_HOURS, 27, 17, 0);   //set your wake-up time here//  SETUP:  minutes/hours/seconds
  RTC.alarmInterrupt(1, true);

void loop() {
  Serial.print("Entering sleep mode");

void Going_To_Sleep(){
    sleep_enable();//Enabling sleep mode
    attachInterrupt(0, wakeUp, LOW);//attaching a interrupt to pin d2
    set_sleep_mode(SLEEP_MODE_PWR_DOWN);//Setting the sleep mode, in our case full sleep
    digitalWrite(ledPin,LOW);//turning LED off
    sleep_cpu();//activating sleep mode
    Serial.println("just woke up!");

    //next line of code executed after the interrupt 
    digitalWrite(ledPin,HIGH);//turning LED on
    digitalWrite(relay, HIGH);

    //Read data and store it to variables hum and temp
    hum = dht.readHumidity();
    therm_mesa= dht.readTemperature();
    digitalWrite(relay, LOW);
    digitalWrite(ledPin, LOW);//turning LED on
    Serial.print("Clearing alarms");
    //When exiting the sleep mode we clear the alarm
    RTC.armAlarm(1, false);
    RTC.alarmInterrupt(1, false);

void wakeUp(){
  Serial.println("Interrrupt Fired");//Print message to serial monitor
  sleep_disable();//Disable sleep mode
  detachInterrupt(0); //Removes the interrupt from pin 2;

void sendSMS(){
  mySerial.println("AT+CMGF=1"); // Configuring TEXT mode
  mySerial.println("AT+CMGS=\"+mobile\"");//change ZZ with country code and xxxxxxxxxxx with phone number to sms
  mySerial.println("Thermokrasia mesa:");
  // End AT command with a ^Z, ASCII code 26
  // Give module time to send SMS

Can you send an SMS without the sleeping?
What to you see on the debug Serial output?
How did you determine it is “skipping it”?

My guess it is either...
a) running it, but it’s not working
b) your module is drawing too much power, and the Arduino is resetting

Start with the simplistic possible example and confirm the SIM module is working. Only then proceed to the next step.

I have tested every part of the code on its own and everything is working fine.The SIM900 is powered from external power source so the power is not an issue.I can send SMS or make a call without a problem when testing the module.
The problem begin when i try to mix the SMS code with the alarm interrupt to arduino from the RTC.
The code is running i have set a led as an output and a relay that the actual project is as debug and the interrupt is firing at the specific time, i see the measurement at serial monitor but the SIM900 can't send the SMS.It seems that for some reason it ignores the sendSMS();.
I tried to disable sleep mode and still nothing happen.I don't know why this is happening as i have used the gsm module with success to other projects.
Any oponion is welcomed.

Are you sure the SIM900 module (or is it a shield?) is powered up (besided the power supply connection) every time you try to communicate with it?

How is the PWRKEY handled? See hardware design for further info SIM900.pdf 4.2.1 section

The AT commands are just "blindly" sent to the module, it would be safer to check for the module response.

It's easy to check how the module answers: tutorial for AT commands or check them in the AT command manual.